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	$39.67	13.140%	$44.8826	$44.88	$44.90	$44.90
Purchase #2	$151.89	6.298%	$161.456	$161.46	$161.45	$161.50
Purchase #3	$58.41	11.533%	$65.1464	$65.15	$65.15	$65.10
Purchase #4	$196.63	11.257%	$218.7646	$218.76	$218.75	$218.80
Purchase #5	$233.31	3.505%	$241.4875	$241.49	$241.50	$241.50
Purchase #6	$59.77	12.524%	$67.2556	$67.26	$67.25	$67.30
Purchase #7	$214.89	9.802%	$235.9535	$235.95	$235.95	$236.00
7 purchase totals =	$954.57		$1,034.9462	$1,034.95	$1,034.95	$1,035.10