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	$77.73	11.438%	$86.6208	$86.62	$86.60	$86.60
Purchase #2	$26.93	9.187%	$29.4041	$29.40	$29.40	$29.40
Purchase #3	$139.47	5.302%	$146.8647	$146.86	$146.85	$146.90
Purchase #4	$240.72	6.417%	$256.167	$256.17	$256.15	$256.20
Purchase #5	$14.82	4.387%	$15.4702	$15.47	$15.45	$15.50
Purchase #6	$52.51	3.395%	$54.2927	$54.29	$54.30	$54.30
Purchase #7	$41.34	8.499%	$44.8535	$44.85	$44.85	$44.90
7 purchase totals =	$593.52		$633.6730	$633.66	$633.60	$633.80