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	$233.97	4.324%	$244.0869	$244.09	$244.10	$244.10
Purchase #2	$203.48	10.168%	$224.1698	$224.17	$224.15	$224.20
Purchase #3	$13.93	12.196%	$15.6289	$15.63	$15.65	$15.60
Purchase #4	$40.67	12.824%	$45.8855	$45.89	$45.90	$45.90
Purchase #5	$180.46	9.188%	$197.0407	$197.04	$197.05	$197.00
Purchase #6	$56.95	13.212%	$64.4742	$64.47	$64.45	$64.50
Purchase #7	$83.81	6.487%	$89.2468	$89.25	$89.25	$89.20
7 purchase totals =	$813.27		$880.5328	$880.54	$880.55	$880.50