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	$217.72	9.504%	$238.4121	$238.41	$238.40	$238.40
Purchase #2	$83.48	12.409%	$93.839	$93.84	$93.85	$93.80
Purchase #3	$108.88	7.749%	$117.3171	$117.32	$117.30	$117.30
Purchase #4	$116.78	9.561%	$127.9453	$127.95	$127.95	$127.90
Purchase #5	$74.32	3.224%	$76.7161	$76.72	$76.70	$76.70
Purchase #6	$100.28	9.307%	$109.6131	$109.61	$109.60	$109.60
Purchase #7	$250.25	13.178%	$283.2279	$283.23	$283.25	$283.20
7 purchase totals =	$951.71		$1,047.0706	$1,047.08	$1,047.05	$1,046.90