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	$92.82	8.310%	$100.5333	$100.53	$100.55	$100.50
Purchase #2	$90.82	9.174%	$99.1518	$99.15	$99.15	$99.20
Purchase #3	$38.37	6.629%	$40.9135	$40.91	$40.90	$40.90
Purchase #4	$201.91	13.669%	$229.5091	$229.51	$229.50	$229.50
Purchase #5	$199.64	12.575%	$224.7447	$224.74	$224.75	$224.70
Purchase #6	$212.70	9.604%	$233.1277	$233.13	$233.15	$233.10
Purchase #7	$234.57	10.572%	$259.3687	$259.37	$259.35	$259.40
7 purchase totals =	$1,070.83		$1,187.3488	$1,187.34	$1,187.35	$1,187.30