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	$194.92	12.696%	$219.667	$219.67	$219.65	$219.70
Purchase #2	$13.50	3.282%	$13.9431	$13.94	$13.95	$13.90
Purchase #3	$62.94	4.870%	$66.0052	$66.01	$66.00	$66.00
Purchase #4	$152.56	12.486%	$171.6086	$171.61	$171.60	$171.60
Purchase #5	$50.94	6.644%	$54.3245	$54.32	$54.30	$54.30
Purchase #6	$211.45	3.130%	$218.0684	$218.07	$218.05	$218.10
Purchase #7	$61.53	6.781%	$65.7023	$65.70	$65.70	$65.70
7 purchase totals =	$747.84		$809.3191	$809.32	$809.25	$809.30