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	$123.33	6.826%	$131.7485	$131.75	$131.75	$131.70
Purchase #2	$216.95	12.155%	$243.3203	$243.32	$243.30	$243.30
Purchase #3	$237.52	7.861%	$256.1914	$256.19	$256.20	$256.20
Purchase #4	$62.77	9.738%	$68.8825	$68.88	$68.90	$68.90
Purchase #5	$136.45	7.674%	$146.9212	$146.92	$146.90	$146.90
Purchase #6	$169.55	7.525%	$182.3086	$182.31	$182.30	$182.30
Purchase #7	$32.84	4.198%	$34.2186	$34.22	$34.20	$34.20
7 purchase totals =	$979.41		$1,063.5911	$1,063.59	$1,063.55	$1,063.50