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	$43.39	4.560%	$45.3686	$45.37	$45.35	$45.40
Purchase #2	$190.37	12.361%	$213.9016	$213.90	$213.90	$213.90
Purchase #3	$135.37	11.393%	$150.7927	$150.79	$150.80	$150.80
Purchase #4	$203.38	9.288%	$222.2699	$222.27	$222.25	$222.30
Purchase #5	$83.64	13.133%	$94.6244	$94.62	$94.60	$94.60
Purchase #6	$50.72	8.494%	$55.0282	$55.03	$55.05	$55.00
Purchase #7	$236.28	9.791%	$259.4142	$259.41	$259.40	$259.40
7 purchase totals =	$943.15		$1,041.3996	$1,041.39	$1,041.35	$1,041.40