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	$74.75	10.618%	$82.687	$82.69	$82.70	$82.70
Purchase #2	$59.41	9.642%	$65.1383	$65.14	$65.15	$65.10
Purchase #3	$58.96	4.564%	$61.6509	$61.65	$61.65	$61.70
Purchase #4	$244.51	3.482%	$253.0238	$253.02	$253.00	$253.00
Purchase #5	$157.78	13.760%	$179.4905	$179.49	$179.50	$179.50
Purchase #6	$78.75	4.501%	$82.2945	$82.29	$82.30	$82.30
Purchase #7	$221.85	4.673%	$232.2171	$232.22	$232.20	$232.20
7 purchase totals =	$896.01		$956.5021	$956.50	$956.50	$956.50