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	$181.54	5.333%	$191.2215	$191.22	$191.20	$191.20
Purchase #2	$80.42	10.194%	$88.618	$88.62	$88.60	$88.60
Purchase #3	$184.77	6.421%	$196.6341	$196.63	$196.65	$196.60
Purchase #4	$207.26	10.399%	$228.813	$228.81	$228.80	$228.80
Purchase #5	$52.56	9.220%	$57.406	$57.41	$57.40	$57.40
Purchase #6	$95.35	4.710%	$99.841	$99.84	$99.85	$99.80
Purchase #7	$143.67	8.651%	$156.0989	$156.10	$156.10	$156.10
7 purchase totals =	$945.57		$1,018.6325	$1,018.63	$1,018.60	$1,018.50