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	$53.71	7.158%	$57.5546	$57.55	$57.55	$57.60
Purchase #2	$70.37	11.394%	$78.388	$78.39	$78.40	$78.40
Purchase #3	$57.32	3.707%	$59.4449	$59.44	$59.45	$59.40
Purchase #4	$5.70	6.478%	$6.0692	$6.07	$6.05	$6.10
Purchase #5	$55.38	5.796%	$58.5898	$58.59	$58.60	$58.60
Purchase #6	$143.40	9.572%	$157.1262	$157.13	$157.15	$157.10
Purchase #7	$141.65	9.502%	$155.1096	$155.11	$155.10	$155.10
7 purchase totals =	$527.53		$572.2823	$572.28	$572.30	$572.30