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	$139.82	4.749%	$146.4601	$146.46	$146.45	$146.50
Purchase #2	$10.90	6.360%	$11.5932	$11.59	$11.60	$11.60
Purchase #3	$130.59	6.781%	$139.4453	$139.45	$139.45	$139.40
Purchase #4	$187.53	5.207%	$197.2947	$197.29	$197.30	$197.30
Purchase #5	$237.97	10.557%	$263.0925	$263.09	$263.10	$263.10
Purchase #6	$239.72	13.764%	$272.7151	$272.72	$272.70	$272.70
Purchase #7	$149.72	5.850%	$158.4786	$158.48	$158.50	$158.50
7 purchase totals =	$1,096.25		$1,189.0795	$1,189.08	$1,189.10	$1,189.10