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	$241.34	5.800%	$255.3377	$255.34	$255.35	$255.30
Purchase #2	$239.95	11.261%	$266.9708	$266.97	$266.95	$267.00
Purchase #3	$40.67	12.359%	$45.6964	$45.70	$45.70	$45.70
Purchase #4	$200.96	8.706%	$218.4556	$218.46	$218.45	$218.50
Purchase #5	$65.25	4.655%	$68.2874	$68.29	$68.30	$68.30
Purchase #6	$72.52	6.803%	$77.4535	$77.45	$77.45	$77.50
Purchase #7	$142.97	7.393%	$153.5398	$153.54	$153.55	$153.50
7 purchase totals =	$1,003.66		$1,085.7412	$1,085.75	$1,085.75	$1,085.80