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	$248.85	8.287%	$269.4722	$269.47	$269.45	$269.50
Purchase #2	$74.34	10.654%	$82.2602	$82.26	$82.25	$82.30
Purchase #3	$131.42	8.604%	$142.7274	$142.73	$142.75	$142.70
Purchase #4	$165.35	11.733%	$184.7505	$184.75	$184.75	$184.80
Purchase #5	$29.68	13.854%	$33.7919	$33.79	$33.80	$33.80
Purchase #6	$98.45	7.554%	$105.8869	$105.89	$105.90	$105.90
Purchase #7	$143.55	3.379%	$148.4006	$148.40	$148.40	$148.40
7 purchase totals =	$891.64		$967.2897	$967.29	$967.30	$967.40