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	$78.98	8.144%	$85.4121	$85.41	$85.40	$85.40
Purchase #2	$130.81	13.640%	$148.6525	$148.65	$148.65	$148.70
Purchase #3	$77.40	11.160%	$86.0378	$86.04	$86.05	$86.00
Purchase #4	$54.92	4.426%	$57.3508	$57.35	$57.35	$57.40
Purchase #5	$32.64	9.638%	$35.7858	$35.79	$35.80	$35.80
Purchase #6	$186.40	5.173%	$196.0425	$196.04	$196.05	$196.00
Purchase #7	$174.51	11.689%	$194.9085	$194.91	$194.90	$194.90
7 purchase totals =	$735.66		$804.1900	$804.19	$804.20	$804.20