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	$67.50	7.162%	$72.3344	$72.33	$72.35	$72.30
Purchase #2	$248.89	4.155%	$259.2314	$259.23	$259.25	$259.20
Purchase #3	$143.25	8.431%	$155.3274	$155.33	$155.35	$155.30
Purchase #4	$61.53	9.510%	$67.3815	$67.38	$67.40	$67.40
Purchase #5	$117.51	10.577%	$129.939	$129.94	$129.95	$129.90
Purchase #6	$234.39	3.628%	$242.8937	$242.89	$242.90	$242.90
Purchase #7	$32.91	10.301%	$36.3001	$36.30	$36.30	$36.30
7 purchase totals =	$905.98		$963.4075	$963.40	$963.50	$963.30