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	$227.84	6.808%	$243.3513	$243.35	$243.35	$243.40
Purchase #2	$61.51	7.784%	$66.2979	$66.30	$66.30	$66.30
Purchase #3	$40.57	7.345%	$43.5499	$43.55	$43.55	$43.50
Purchase #4	$174.87	8.255%	$189.3055	$189.31	$189.30	$189.30
Purchase #5	$52.42	11.495%	$58.4457	$58.45	$58.45	$58.40
Purchase #6	$149.86	3.484%	$155.0811	$155.08	$155.10	$155.10
Purchase #7	$188.49	11.172%	$209.5481	$209.55	$209.55	$209.50
7 purchase totals =	$895.56		$965.5795	$965.59	$965.60	$965.50