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	$168.42	6.778%	$179.8355	$179.84	$179.85	$179.80
Purchase #2	$70.49	3.685%	$73.0876	$73.09	$73.10	$73.10
Purchase #3	$56.72	10.459%	$62.6523	$62.65	$62.65	$62.70
Purchase #4	$89.56	13.276%	$101.45	$101.45	$101.45	$101.50
Purchase #5	$81.39	9.430%	$89.0651	$89.07	$89.05	$89.10
Purchase #6	$165.38	8.300%	$179.1065	$179.11	$179.10	$179.10
Purchase #7	$106.38	11.806%	$118.9392	$118.94	$118.95	$118.90
7 purchase totals =	$738.34		$804.1362	$804.15	$804.15	$804.20