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	$67.27	7.185%	$72.1033	$72.10	$72.10	$72.10
Purchase #2	$38.98	8.187%	$42.1713	$42.17	$42.15	$42.20
Purchase #3	$159.78	9.716%	$175.3042	$175.30	$175.30	$175.30
Purchase #4	$183.64	9.126%	$200.399	$200.40	$200.40	$200.40
Purchase #5	$74.71	4.284%	$77.9106	$77.91	$77.90	$77.90
Purchase #6	$240.67	6.670%	$256.7227	$256.72	$256.70	$256.70
Purchase #7	$36.60	3.775%	$37.9817	$37.98	$38.00	$38.00
7 purchase totals =	$801.65		$862.5928	$862.58	$862.55	$862.60