Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$223.43	11.714%	$249.6026	$249.60	$249.60	$249.60
Purchase #2	$57.26	12.827%	$64.6047	$64.60	$64.60	$64.60
Purchase #3	$86.75	11.564%	$96.7818	$96.78	$96.80	$96.80
Purchase #4	$47.99	11.274%	$53.4004	$53.40	$53.40	$53.40
Purchase #5	$144.66	10.809%	$160.2963	$160.30	$160.30	$160.30
Purchase #6	$232.31	11.317%	$258.6005	$258.60	$258.60	$258.60
Purchase #7	$171.64	5.570%	$181.2003	$181.20	$181.20	$181.20
7 purchase totals =	$964.04		$1,064.4866	$1,064.48	$1,064.50	$1,064.50