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	$96.64	3.117%	$99.6523	$99.65	$99.65	$99.70
Purchase #2	$83.97	4.667%	$87.8889	$87.89	$87.90	$87.90
Purchase #3	$238.77	4.830%	$250.3026	$250.30	$250.30	$250.30
Purchase #4	$175.38	9.712%	$192.4129	$192.41	$192.40	$192.40
Purchase #5	$77.92	13.584%	$88.5047	$88.50	$88.50	$88.50
Purchase #6	$200.38	7.401%	$215.2101	$215.21	$215.20	$215.20
Purchase #7	$112.51	8.821%	$122.4345	$122.43	$122.45	$122.40
7 purchase totals =	$985.57		$1,056.4060	$1,056.39	$1,056.40	$1,056.40