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	$127.30	12.115%	$142.7224	$142.72	$142.70	$142.70
Purchase #2	$174.87	4.594%	$182.9035	$182.90	$182.90	$182.90
Purchase #3	$152.81	4.580%	$159.8087	$159.81	$159.80	$159.80
Purchase #4	$131.25	5.285%	$138.1866	$138.19	$138.20	$138.20
Purchase #5	$151.80	13.419%	$172.17	$172.17	$172.15	$172.20
Purchase #6	$97.91	7.510%	$105.263	$105.26	$105.25	$105.30
Purchase #7	$208.35	13.475%	$236.4252	$236.43	$236.45	$236.40
7 purchase totals =	$1,044.29		$1,137.4794	$1,137.48	$1,137.45	$1,137.50