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	$130.56	12.407%	$146.7586	$146.76	$146.75	$146.80
Purchase #2	$223.67	7.517%	$240.4833	$240.48	$240.50	$240.50
Purchase #3	$101.70	10.480%	$112.3582	$112.36	$112.35	$112.40
Purchase #4	$214.45	6.250%	$227.8531	$227.85	$227.85	$227.90
Purchase #5	$130.52	11.744%	$145.8483	$145.85	$145.85	$145.80
Purchase #6	$179.70	10.461%	$198.4984	$198.50	$198.50	$198.50
Purchase #7	$232.29	10.546%	$256.7873	$256.79	$256.80	$256.80
7 purchase totals =	$1,212.89		$1,328.5872	$1,328.59	$1,328.60	$1,328.70