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	$212.44	6.109%	$225.418	$225.42	$225.40	$225.40
Purchase #2	$117.72	11.123%	$130.814	$130.81	$130.80	$130.80
Purchase #3	$169.71	6.550%	$180.826	$180.83	$180.85	$180.80
Purchase #4	$35.92	4.495%	$37.5346	$37.53	$37.55	$37.50
Purchase #5	$135.25	12.811%	$152.5769	$152.58	$152.60	$152.60
Purchase #6	$246.30	5.716%	$260.3785	$260.38	$260.40	$260.40
Purchase #7	$212.59	10.710%	$235.3584	$235.36	$235.35	$235.40
7 purchase totals =	$1,129.93		$1,222.9064	$1,222.91	$1,222.95	$1,222.90