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	$54.28	6.642%	$57.8853	$57.89	$57.90	$57.90
Purchase #2	$68.50	4.393%	$71.5092	$71.51	$71.50	$71.50
Purchase #3	$51.39	13.561%	$58.359	$58.36	$58.35	$58.40
Purchase #4	$248.54	9.401%	$271.9052	$271.91	$271.90	$271.90
Purchase #5	$223.77	12.501%	$251.7435	$251.74	$251.75	$251.70
Purchase #6	$239.95	8.313%	$259.897	$259.90	$259.90	$259.90
Purchase #7	$78.57	11.756%	$87.8067	$87.81	$87.80	$87.80
7 purchase totals =	$965.00		$1,059.1059	$1,059.12	$1,059.10	$1,059.10