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	$57.78	4.591%	$60.4327	$60.43	$60.45	$60.40
Purchase #2	$17.53	5.289%	$18.4572	$18.46	$18.45	$18.50
Purchase #3	$72.29	3.507%	$74.8252	$74.83	$74.85	$74.80
Purchase #4	$234.64	9.339%	$256.553	$256.55	$256.55	$256.60
Purchase #5	$57.28	4.523%	$59.8708	$59.87	$59.85	$59.90
Purchase #6	$220.38	10.313%	$243.1078	$243.11	$243.10	$243.10
Purchase #7	$143.93	12.219%	$161.5168	$161.52	$161.50	$161.50
7 purchase totals =	$803.83		$874.7635	$874.77	$874.75	$874.80