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	$53.28	11.626%	$59.4743	$59.47	$59.45	$59.50
Purchase #2	$237.62	8.103%	$256.8743	$256.87	$256.85	$256.90
Purchase #3	$124.89	12.698%	$140.7485	$140.75	$140.75	$140.70
Purchase #4	$133.62	12.659%	$150.535	$150.54	$150.55	$150.50
Purchase #5	$125.99	4.521%	$131.686	$131.69	$131.70	$131.70
Purchase #6	$135.96	12.847%	$153.4268	$153.43	$153.45	$153.40
Purchase #7	$232.50	3.459%	$240.5422	$240.54	$240.55	$240.50
7 purchase totals =	$1,043.86		$1,133.2871	$1,133.29	$1,133.30	$1,133.20