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	$84.33	7.857%	$90.9558	$90.96	$90.95	$91.00
Purchase #2	$133.95	10.514%	$148.0335	$148.03	$148.05	$148.00
Purchase #3	$10.72	13.489%	$12.166	$12.17	$12.15	$12.20
Purchase #4	$91.93	3.512%	$95.1586	$95.16	$95.15	$95.20
Purchase #5	$199.72	12.443%	$224.5712	$224.57	$224.55	$224.60
Purchase #6	$75.88	12.778%	$85.5759	$85.58	$85.60	$85.60
Purchase #7	$151.63	3.167%	$156.4321	$156.43	$156.45	$156.40
7 purchase totals =	$748.16		$812.8931	$812.90	$812.90	$813.00