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	$199.98	13.363%	$226.7033	$226.70	$226.70	$226.70
Purchase #2	$231.37	4.662%	$242.1565	$242.16	$242.15	$242.20
Purchase #3	$82.77	9.584%	$90.7027	$90.70	$90.70	$90.70
Purchase #4	$191.99	4.411%	$200.4587	$200.46	$200.45	$200.50
Purchase #5	$140.36	5.111%	$147.5338	$147.53	$147.55	$147.50
Purchase #6	$41.69	9.168%	$45.5121	$45.51	$45.50	$45.50
Purchase #7	$51.67	3.574%	$53.5167	$53.52	$53.50	$53.50
7 purchase totals =	$939.83		$1,006.5838	$1,006.58	$1,006.55	$1,006.60