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	$242.79	10.244%	$267.6614	$267.66	$267.65	$267.70
Purchase #2	$167.47	10.536%	$185.1146	$185.11	$185.10	$185.10
Purchase #3	$242.32	13.566%	$275.1931	$275.19	$275.20	$275.20
Purchase #4	$172.42	3.720%	$178.834	$178.83	$178.85	$178.80
Purchase #5	$90.69	9.721%	$99.506	$99.51	$99.50	$99.50
Purchase #6	$75.79	7.494%	$81.4697	$81.47	$81.45	$81.50
Purchase #7	$40.25	9.197%	$43.9518	$43.95	$43.95	$44.00
7 purchase totals =	$1,031.73		$1,131.7306	$1,131.72	$1,131.70	$1,131.80