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	$93.47	3.228%	$96.4872	$96.49	$96.50	$96.50
Purchase #2	$27.57	7.529%	$29.6457	$29.65	$29.65	$29.60
Purchase #3	$139.90	9.140%	$152.6869	$152.69	$152.70	$152.70
Purchase #4	$67.30	6.294%	$71.5359	$71.54	$71.55	$71.50
Purchase #5	$41.25	9.482%	$45.1613	$45.16	$45.15	$45.20
Purchase #6	$214.63	10.195%	$236.5115	$236.51	$236.50	$236.50
Purchase #7	$83.33	11.174%	$92.6413	$92.64	$92.65	$92.60
7 purchase totals =	$667.45		$724.6698	$724.68	$724.70	$724.60