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	$9.25	10.224%	$10.1957	$10.20	$10.20	$10.20
Purchase #2	$172.40	11.116%	$191.564	$191.56	$191.55	$191.60
Purchase #3	$179.92	9.229%	$196.5248	$196.52	$196.50	$196.50
Purchase #4	$223.89	10.129%	$246.5678	$246.57	$246.55	$246.60
Purchase #5	$56.60	12.222%	$63.5177	$63.52	$63.50	$63.50
Purchase #6	$29.65	9.428%	$32.4454	$32.45	$32.45	$32.40
Purchase #7	$208.26	9.315%	$227.6594	$227.66	$227.65	$227.70
7 purchase totals =	$879.97		$968.4748	$968.48	$968.40	$968.50