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	$100.29	5.597%	$105.9032	$105.90	$105.90	$105.90
Purchase #2	$156.33	10.738%	$173.1167	$173.12	$173.10	$173.10
Purchase #3	$14.34	5.286%	$15.098	$15.10	$15.10	$15.10
Purchase #4	$14.70	5.590%	$15.5217	$15.52	$15.50	$15.50
Purchase #5	$240.75	3.245%	$248.5623	$248.56	$248.55	$248.60
Purchase #6	$86.67	7.690%	$93.3349	$93.33	$93.35	$93.30
Purchase #7	$59.70	13.574%	$67.8037	$67.80	$67.80	$67.80
7 purchase totals =	$672.78		$719.3405	$719.33	$719.30	$719.30