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	$81.73	8.157%	$88.3967	$88.40	$88.40	$88.40
Purchase #2	$38.27	5.874%	$40.518	$40.52	$40.50	$40.50
Purchase #3	$202.46	7.381%	$217.4036	$217.40	$217.40	$217.40
Purchase #4	$34.33	8.291%	$37.1763	$37.18	$37.20	$37.20
Purchase #5	$88.88	4.808%	$93.1534	$93.15	$93.15	$93.20
Purchase #6	$38.47	6.156%	$40.8382	$40.84	$40.85	$40.80
Purchase #7	$200.71	4.554%	$209.8503	$209.85	$209.85	$209.90
7 purchase totals =	$684.85		$727.3365	$727.34	$727.35	$727.40