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	$200.32	11.125%	$222.6056	$222.61	$222.60	$222.60
Purchase #2	$234.92	11.155%	$261.1253	$261.13	$261.15	$261.10
Purchase #3	$247.36	12.473%	$278.2132	$278.21	$278.20	$278.20
Purchase #4	$98.33	13.347%	$111.4541	$111.45	$111.45	$111.50
Purchase #5	$112.29	10.869%	$124.4948	$124.49	$124.50	$124.50
Purchase #6	$90.36	4.556%	$94.4768	$94.48	$94.50	$94.50
Purchase #7	$154.77	12.102%	$173.5003	$173.50	$173.50	$173.50
7 purchase totals =	$1,138.35		$1,265.8701	$1,265.87	$1,265.90	$1,265.90