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	$127.25	4.269%	$132.6823	$132.68	$132.70	$132.70
Purchase #2	$148.33	11.676%	$165.649	$165.65	$165.65	$165.60
Purchase #3	$112.52	11.102%	$125.012	$125.01	$125.00	$125.00
Purchase #4	$44.52	11.840%	$49.7912	$49.79	$49.80	$49.80
Purchase #5	$222.66	12.198%	$249.8201	$249.82	$249.80	$249.80
Purchase #6	$80.28	11.600%	$89.5925	$89.59	$89.60	$89.60
Purchase #7	$218.86	13.205%	$247.7605	$247.76	$247.75	$247.80
7 purchase totals =	$954.42		$1,060.3076	$1,060.30	$1,060.30	$1,060.30