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	$208.51	9.665%	$228.6625	$228.66	$228.65	$228.70
Purchase #2	$89.65	6.439%	$95.4226	$95.42	$95.40	$95.40
Purchase #3	$59.34	5.147%	$62.3942	$62.39	$62.40	$62.40
Purchase #4	$72.87	5.390%	$76.7977	$76.80	$76.80	$76.80
Purchase #5	$159.64	3.540%	$165.2913	$165.29	$165.30	$165.30
Purchase #6	$155.83	5.174%	$163.8926	$163.89	$163.90	$163.90
Purchase #7	$193.80	8.289%	$209.8641	$209.86	$209.85	$209.90
7 purchase totals =	$939.64		$1,002.3250	$1,002.31	$1,002.30	$1,002.40