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	$186.96	12.254%	$209.8701	$209.87	$209.85	$209.90
Purchase #2	$104.45	13.432%	$118.4797	$118.48	$118.50	$118.50
Purchase #3	$155.44	11.255%	$172.9348	$172.93	$172.95	$172.90
Purchase #4	$42.59	13.769%	$48.4542	$48.45	$48.45	$48.50
Purchase #5	$212.98	5.718%	$225.1582	$225.16	$225.15	$225.20
Purchase #6	$124.45	6.793%	$132.9039	$132.90	$132.90	$132.90
Purchase #7	$41.83	12.470%	$47.0462	$47.05	$47.05	$47.00
7 purchase totals =	$868.70		$954.8471	$954.84	$954.85	$954.90