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	$31.65	4.799%	$33.1689	$33.17	$33.15	$33.20
Purchase #2	$76.79	12.733%	$86.5677	$86.57	$86.55	$86.60
Purchase #3	$80.27	11.278%	$89.3229	$89.32	$89.30	$89.30
Purchase #4	$235.61	11.345%	$262.34	$262.34	$262.35	$262.30
Purchase #5	$153.88	4.709%	$161.1262	$161.13	$161.15	$161.10
Purchase #6	$247.25	6.494%	$263.3064	$263.31	$263.30	$263.30
Purchase #7	$54.30	10.174%	$59.8245	$59.82	$59.80	$59.80
7 purchase totals =	$879.75		$955.6566	$955.66	$955.60	$955.60