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	$221.38	9.472%	$242.3491	$242.35	$242.35	$242.30
Purchase #2	$66.27	4.617%	$69.3297	$69.33	$69.35	$69.30
Purchase #3	$65.81	8.157%	$71.1781	$71.18	$71.20	$71.20
Purchase #4	$200.40	9.474%	$219.3859	$219.39	$219.40	$219.40
Purchase #5	$37.36	12.654%	$42.0875	$42.09	$42.10	$42.10
Purchase #6	$46.43	13.547%	$52.7199	$52.72	$52.70	$52.70
Purchase #7	$36.95	12.255%	$41.4782	$41.48	$41.50	$41.50
7 purchase totals =	$674.60		$738.5284	$738.54	$738.60	$738.50