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	$196.58	11.254%	$218.7031	$218.70	$218.70	$218.70
Purchase #2	$37.72	13.205%	$42.7009	$42.70	$42.70	$42.70
Purchase #3	$188.71	10.681%	$208.8661	$208.87	$208.85	$208.90
Purchase #4	$105.42	4.243%	$109.893	$109.89	$109.90	$109.90
Purchase #5	$162.59	7.813%	$175.2932	$175.29	$175.30	$175.30
Purchase #6	$138.44	8.478%	$150.1769	$150.18	$150.20	$150.20
Purchase #7	$206.89	5.219%	$217.6876	$217.69	$217.70	$217.70
7 purchase totals =	$1,036.35		$1,123.3208	$1,123.32	$1,123.35	$1,123.40