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	$158.30	7.523%	$170.2089	$170.21	$170.20	$170.20
Purchase #2	$78.96	7.748%	$85.0778	$85.08	$85.10	$85.10
Purchase #3	$181.58	5.499%	$191.5651	$191.57	$191.55	$191.60
Purchase #4	$52.65	6.284%	$55.9585	$55.96	$55.95	$56.00
Purchase #5	$227.25	12.361%	$255.3404	$255.34	$255.35	$255.30
Purchase #6	$230.45	7.824%	$248.4804	$248.48	$248.50	$248.50
Purchase #7	$237.52	7.573%	$255.5074	$255.51	$255.50	$255.50
7 purchase totals =	$1,166.71		$1,262.1385	$1,262.15	$1,262.15	$1,262.20