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	$66.49	7.434%	$71.4329	$71.43	$71.45	$71.40
Purchase #2	$237.51	13.435%	$269.4195	$269.42	$269.40	$269.40
Purchase #3	$167.53	9.810%	$183.9647	$183.96	$183.95	$184.00
Purchase #4	$208.96	4.751%	$218.8877	$218.89	$218.90	$218.90
Purchase #5	$140.53	13.840%	$159.9794	$159.98	$160.00	$160.00
Purchase #6	$162.94	11.627%	$181.885	$181.89	$181.90	$181.90
Purchase #7	$62.54	3.485%	$64.7195	$64.72	$64.70	$64.70
7 purchase totals =	$1,046.50		$1,150.2887	$1,150.29	$1,150.30	$1,150.30