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	$211.95	5.450%	$223.5013	$223.50	$223.50	$223.50
Purchase #2	$148.83	6.278%	$158.1735	$158.17	$158.15	$158.20
Purchase #3	$154.47	13.709%	$175.6463	$175.65	$175.65	$175.60
Purchase #4	$185.91	12.611%	$209.3551	$209.36	$209.35	$209.40
Purchase #5	$20.41	3.238%	$21.0709	$21.07	$21.05	$21.10
Purchase #6	$230.38	11.519%	$256.9175	$256.92	$256.90	$256.90
Purchase #7	$33.29	10.441%	$36.7658	$36.77	$36.75	$36.80
7 purchase totals =	$985.24		$1,081.4304	$1,081.44	$1,081.35	$1,081.50