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	$92.41	3.133%	$95.3052	$95.31	$95.30	$95.30
Purchase #2	$149.52	10.773%	$165.6278	$165.63	$165.65	$165.60
Purchase #3	$48.45	13.659%	$55.0678	$55.07	$55.05	$55.10
Purchase #4	$213.78	11.467%	$238.2942	$238.29	$238.30	$238.30
Purchase #5	$201.33	7.353%	$216.1338	$216.13	$216.15	$216.10
Purchase #6	$207.53	5.105%	$218.1244	$218.12	$218.10	$218.10
Purchase #7	$152.87	9.167%	$166.8836	$166.88	$166.90	$166.90
7 purchase totals =	$1,065.89		$1,155.4368	$1,155.43	$1,155.45	$1,155.40