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	$100.72	9.689%	$110.4788	$110.48	$110.50	$110.50
Purchase #2	$31.68	7.703%	$34.1203	$34.12	$34.10	$34.10
Purchase #3	$146.89	5.643%	$155.179	$155.18	$155.20	$155.20
Purchase #4	$19.71	6.841%	$21.0584	$21.06	$21.05	$21.10
Purchase #5	$60.78	6.123%	$64.5016	$64.50	$64.50	$64.50
Purchase #6	$52.49	12.694%	$59.1531	$59.15	$59.15	$59.20
Purchase #7	$10.53	9.471%	$11.5273	$11.53	$11.55	$11.50
7 purchase totals =	$422.80		$456.0185	$456.02	$456.05	$456.10