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	$152.81	3.579%	$158.2791	$158.28	$158.30	$158.30
Purchase #2	$175.83	6.562%	$187.368	$187.37	$187.35	$187.40
Purchase #3	$33.57	12.500%	$37.7663	$37.77	$37.75	$37.80
Purchase #4	$57.31	13.144%	$64.8428	$64.84	$64.85	$64.80
Purchase #5	$95.36	9.619%	$104.5327	$104.53	$104.55	$104.50
Purchase #6	$229.91	13.443%	$260.8168	$260.82	$260.80	$260.80
Purchase #7	$65.53	9.550%	$71.7881	$71.79	$71.80	$71.80
7 purchase totals =	$810.32		$885.3938	$885.40	$885.40	$885.40