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	$223.51	4.256%	$233.0226	$233.02	$233.00	$233.00
Purchase #2	$65.45	9.248%	$71.5028	$71.50	$71.50	$71.50
Purchase #3	$67.48	13.152%	$76.355	$76.36	$76.35	$76.40
Purchase #4	$63.42	8.227%	$68.6376	$68.64	$68.65	$68.60
Purchase #5	$36.78	8.161%	$39.7816	$39.78	$39.80	$39.80
Purchase #6	$37.56	5.669%	$39.6893	$39.69	$39.70	$39.70
Purchase #7	$69.25	13.293%	$78.4554	$78.46	$78.45	$78.50
7 purchase totals =	$563.45		$607.4443	$607.45	$607.45	$607.50