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	$63.30	13.208%	$71.6607	$71.66	$71.65	$71.70
Purchase #2	$111.61	13.753%	$126.9597	$126.96	$126.95	$127.00
Purchase #3	$223.77	12.221%	$251.1169	$251.12	$251.10	$251.10
Purchase #4	$243.71	3.295%	$251.7402	$251.74	$251.75	$251.70
Purchase #5	$126.81	7.584%	$136.4273	$136.43	$136.45	$136.40
Purchase #6	$90.38	4.430%	$94.3838	$94.38	$94.40	$94.40
Purchase #7	$65.54	9.147%	$71.5349	$71.53	$71.55	$71.50
7 purchase totals =	$925.12		$1,003.8235	$1,003.82	$1,003.85	$1,003.80