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	$67.79	5.527%	$71.5368	$71.54	$71.55	$71.50
Purchase #2	$188.29	12.355%	$211.5532	$211.55	$211.55	$211.60
Purchase #3	$223.44	8.622%	$242.705	$242.71	$242.70	$242.70
Purchase #4	$159.89	3.451%	$165.4078	$165.41	$165.40	$165.40
Purchase #5	$139.72	8.684%	$151.8533	$151.85	$151.85	$151.90
Purchase #6	$225.51	11.179%	$250.7198	$250.72	$250.70	$250.70
Purchase #7	$126.94	7.849%	$136.9035	$136.90	$136.90	$136.90
7 purchase totals =	$1,131.58		$1,230.6794	$1,230.68	$1,230.65	$1,230.70