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	$52.69	4.591%	$55.109	$55.11	$55.10	$55.10
Purchase #2	$99.62	4.114%	$103.7184	$103.72	$103.70	$103.70
Purchase #3	$97.73	13.808%	$111.2246	$111.22	$111.20	$111.20
Purchase #4	$248.61	3.171%	$256.4934	$256.49	$256.50	$256.50
Purchase #5	$146.91	7.235%	$157.5389	$157.54	$157.55	$157.50
Purchase #6	$80.39	6.173%	$85.3525	$85.35	$85.35	$85.40
Purchase #7	$183.92	7.733%	$198.1425	$198.14	$198.15	$198.10
7 purchase totals =	$909.87		$967.5793	$967.57	$967.55	$967.50