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	$172.61	13.790%	$196.4129	$196.41	$196.40	$196.40
Purchase #2	$65.67	7.850%	$70.8251	$70.83	$70.85	$70.80
Purchase #3	$128.47	6.605%	$136.9554	$136.96	$136.95	$137.00
Purchase #4	$165.79	6.405%	$176.4088	$176.41	$176.40	$176.40
Purchase #5	$30.96	9.449%	$33.8854	$33.89	$33.90	$33.90
Purchase #6	$237.52	8.840%	$258.5168	$258.52	$258.50	$258.50
Purchase #7	$162.75	10.258%	$179.4449	$179.44	$179.45	$179.40
7 purchase totals =	$963.77		$1,052.4493	$1,052.46	$1,052.45	$1,052.40