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	$54.42	5.275%	$57.2907	$57.29	$57.30	$57.30
Purchase #2	$84.37	10.851%	$93.525	$93.53	$93.55	$93.50
Purchase #3	$122.56	9.155%	$133.7804	$133.78	$133.80	$133.80
Purchase #4	$89.88	10.294%	$99.1322	$99.13	$99.15	$99.10
Purchase #5	$244.60	4.454%	$255.4945	$255.49	$255.50	$255.50
Purchase #6	$22.35	9.673%	$24.5119	$24.51	$24.50	$24.50
Purchase #7	$203.79	13.576%	$231.4565	$231.46	$231.45	$231.50
7 purchase totals =	$821.97		$895.1912	$895.19	$895.25	$895.20