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	$206.79	11.672%	$230.9265	$230.93	$230.95	$230.90
Purchase #2	$34.72	6.770%	$37.0705	$37.07	$37.05	$37.10
Purchase #3	$102.43	11.843%	$114.5608	$114.56	$114.55	$114.60
Purchase #4	$69.43	12.668%	$78.2254	$78.23	$78.25	$78.20
Purchase #5	$39.69	4.810%	$41.5991	$41.60	$41.60	$41.60
Purchase #6	$51.65	13.455%	$58.5995	$58.60	$58.60	$58.60
Purchase #7	$37.62	8.171%	$40.6939	$40.69	$40.70	$40.70
7 purchase totals =	$542.33		$601.6757	$601.68	$601.70	$601.70