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	$161.81	11.559%	$180.5136	$180.51	$180.50	$180.50
Purchase #2	$130.48	11.168%	$145.052	$145.05	$145.05	$145.10
Purchase #3	$108.37	7.807%	$116.8304	$116.83	$116.85	$116.80
Purchase #4	$189.90	11.491%	$211.7214	$211.72	$211.70	$211.70
Purchase #5	$146.43	9.213%	$159.9206	$159.92	$159.90	$159.90
Purchase #6	$99.29	10.311%	$109.5278	$109.53	$109.55	$109.50
Purchase #7	$154.58	10.751%	$171.1989	$171.20	$171.20	$171.20
7 purchase totals =	$990.86		$1,094.7647	$1,094.76	$1,094.75	$1,094.70