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	$228.75	11.259%	$254.505	$254.51	$254.50	$254.50
Purchase #2	$195.71	6.295%	$208.0299	$208.03	$208.05	$208.00
Purchase #3	$142.89	9.653%	$156.6832	$156.68	$156.70	$156.70
Purchase #4	$131.53	4.365%	$137.2713	$137.27	$137.25	$137.30
Purchase #5	$30.48	6.852%	$32.5685	$32.57	$32.55	$32.60
Purchase #6	$90.43	10.542%	$99.9631	$99.96	$99.95	$100.00
Purchase #7	$187.26	6.508%	$199.4469	$199.45	$199.45	$199.40
7 purchase totals =	$1,007.05		$1,088.4679	$1,088.47	$1,088.45	$1,088.50