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	$106.42	7.580%	$114.4866	$114.49	$114.50	$114.50
Purchase #2	$10.32	10.420%	$11.3953	$11.40	$11.40	$11.40
Purchase #3	$195.87	4.388%	$204.4648	$204.46	$204.45	$204.50
Purchase #4	$45.92	12.188%	$51.5167	$51.52	$51.50	$51.50
Purchase #5	$96.53	9.727%	$105.9195	$105.92	$105.90	$105.90
Purchase #6	$68.55	5.735%	$72.4813	$72.48	$72.50	$72.50
Purchase #7	$200.59	4.540%	$209.6968	$209.70	$209.70	$209.70
7 purchase totals =	$724.20		$769.9610	$769.97	$769.95	$770.00