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	$151.53	9.425%	$165.8117	$165.81	$165.80	$165.80
Purchase #2	$230.29	13.426%	$261.2087	$261.21	$261.20	$261.20
Purchase #3	$119.95	6.409%	$127.6376	$127.64	$127.65	$127.60
Purchase #4	$45.26	7.783%	$48.7826	$48.78	$48.80	$48.80
Purchase #5	$168.78	9.873%	$185.4436	$185.44	$185.45	$185.40
Purchase #6	$237.38	3.428%	$245.5174	$245.52	$245.50	$245.50
Purchase #7	$152.59	13.310%	$172.8997	$172.90	$172.90	$172.90
7 purchase totals =	$1,105.78		$1,207.3013	$1,207.30	$1,207.30	$1,207.20