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	$89.64	4.632%	$93.7921	$93.79	$93.80	$93.80
Purchase #2	$224.42	8.412%	$243.2982	$243.30	$243.30	$243.30
Purchase #3	$222.83	11.409%	$248.2527	$248.25	$248.25	$248.30
Purchase #4	$14.69	3.587%	$15.2169	$15.22	$15.20	$15.20
Purchase #5	$198.32	10.158%	$218.4653	$218.47	$218.45	$218.50
Purchase #6	$52.47	8.431%	$56.8937	$56.89	$56.90	$56.90
Purchase #7	$135.90	5.602%	$143.5131	$143.51	$143.50	$143.50
7 purchase totals =	$938.27		$1,019.4320	$1,019.43	$1,019.40	$1,019.50