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	$243.48	3.301%	$251.5173	$251.52	$251.50	$251.50
Purchase #2	$243.51	5.340%	$256.5134	$256.51	$256.50	$256.50
Purchase #3	$205.43	13.752%	$233.6807	$233.68	$233.70	$233.70
Purchase #4	$186.67	13.209%	$211.3272	$211.33	$211.35	$211.30
Purchase #5	$202.52	5.307%	$213.2677	$213.27	$213.25	$213.30
Purchase #6	$52.62	6.291%	$55.9303	$55.93	$55.95	$55.90
Purchase #7	$146.50	11.146%	$162.8289	$162.83	$162.85	$162.80
7 purchase totals =	$1,280.73		$1,385.0655	$1,385.07	$1,385.10	$1,385.00