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	$232.92	9.293%	$254.5653	$254.57	$254.55	$254.60
Purchase #2	$74.75	5.331%	$78.7349	$78.73	$78.75	$78.70
Purchase #3	$26.43	7.222%	$28.3388	$28.34	$28.35	$28.30
Purchase #4	$33.61	10.873%	$37.2644	$37.26	$37.25	$37.30
Purchase #5	$215.31	9.168%	$235.0496	$235.05	$235.05	$235.00
Purchase #6	$236.45	3.334%	$244.3332	$244.33	$244.35	$244.30
Purchase #7	$71.80	9.826%	$78.8551	$78.86	$78.85	$78.90
7 purchase totals =	$891.27		$957.1413	$957.14	$957.15	$957.10