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	$146.72	13.216%	$166.1105	$166.11	$166.10	$166.10
Purchase #2	$188.95	10.375%	$208.5536	$208.55	$208.55	$208.60
Purchase #3	$137.78	12.578%	$155.11	$155.11	$155.10	$155.10
Purchase #4	$242.89	13.552%	$275.8065	$275.81	$275.80	$275.80
Purchase #5	$34.37	4.224%	$35.8218	$35.82	$35.80	$35.80
Purchase #6	$49.30	13.335%	$55.8742	$55.87	$55.85	$55.90
Purchase #7	$180.77	9.593%	$198.1113	$198.11	$198.10	$198.10
7 purchase totals =	$980.78		$1,095.3879	$1,095.38	$1,095.30	$1,095.40