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	$239.97	4.293%	$250.2719	$250.27	$250.25	$250.30
Purchase #2	$60.92	9.716%	$66.839	$66.84	$66.85	$66.80
Purchase #3	$243.74	11.277%	$271.2266	$271.23	$271.25	$271.20
Purchase #4	$75.37	10.559%	$83.3283	$83.33	$83.35	$83.30
Purchase #5	$38.80	9.502%	$42.4868	$42.49	$42.50	$42.50
Purchase #6	$231.45	10.733%	$256.2915	$256.29	$256.30	$256.30
Purchase #7	$70.71	7.866%	$76.272	$76.27	$76.25	$76.30
7 purchase totals =	$960.96		$1,046.7161	$1,046.72	$1,046.75	$1,046.70