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	$93.72	11.761%	$104.7424	$104.74	$104.75	$104.70
Purchase #2	$103.78	9.361%	$113.4948	$113.49	$113.50	$113.50
Purchase #3	$84.51	6.160%	$89.7158	$89.72	$89.70	$89.70
Purchase #4	$235.90	9.460%	$258.2161	$258.22	$258.20	$258.20
Purchase #5	$139.65	13.195%	$158.0768	$158.08	$158.10	$158.10
Purchase #6	$216.25	12.689%	$243.69	$243.69	$243.70	$243.70
Purchase #7	$160.66	3.855%	$166.8534	$166.85	$166.85	$166.90
7 purchase totals =	$1,034.47		$1,134.7893	$1,134.79	$1,134.80	$1,134.80