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	$234.44	7.184%	$251.2822	$251.28	$251.30	$251.30
Purchase #2	$208.67	7.148%	$223.5857	$223.59	$223.60	$223.60
Purchase #3	$64.60	3.504%	$66.8636	$66.86	$66.85	$66.90
Purchase #4	$39.96	8.335%	$43.2907	$43.29	$43.30	$43.30
Purchase #5	$74.36	10.289%	$82.0109	$82.01	$82.00	$82.00
Purchase #6	$138.79	10.762%	$153.7266	$153.73	$153.75	$153.70
Purchase #7	$198.72	12.418%	$223.397	$223.40	$223.40	$223.40
7 purchase totals =	$959.54		$1,044.1567	$1,044.16	$1,044.20	$1,044.20