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	$143.82	6.628%	$153.3524	$153.35	$153.35	$153.40
Purchase #2	$209.79	6.217%	$222.8326	$222.83	$222.85	$222.80
Purchase #3	$227.88	13.424%	$258.4706	$258.47	$258.45	$258.50
Purchase #4	$63.44	10.748%	$70.2585	$70.26	$70.25	$70.30
Purchase #5	$157.38	9.779%	$172.7702	$172.77	$172.75	$172.80
Purchase #6	$47.89	10.551%	$52.9429	$52.94	$52.95	$52.90
Purchase #7	$133.35	7.639%	$143.5366	$143.54	$143.55	$143.50
7 purchase totals =	$983.55		$1,074.1638	$1,074.16	$1,074.15	$1,074.20