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	$134.74	12.258%	$151.2564	$151.26	$151.25	$151.30
Purchase #2	$145.79	6.399%	$155.1191	$155.12	$155.10	$155.10
Purchase #3	$73.31	10.226%	$80.8067	$80.81	$80.80	$80.80
Purchase #4	$26.50	3.261%	$27.3642	$27.36	$27.35	$27.40
Purchase #5	$172.77	13.858%	$196.7125	$196.71	$196.70	$196.70
Purchase #6	$68.82	11.569%	$76.7818	$76.78	$76.80	$76.80
Purchase #7	$141.58	3.513%	$146.5537	$146.55	$146.55	$146.60
7 purchase totals =	$763.51		$834.5944	$834.59	$834.55	$834.70