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	$199.94	7.252%	$214.4396	$214.44	$214.45	$214.40
Purchase #2	$221.88	11.332%	$247.0234	$247.02	$247.00	$247.00
Purchase #3	$108.46	9.241%	$118.4828	$118.48	$118.50	$118.50
Purchase #4	$119.49	7.837%	$128.8544	$128.85	$128.85	$128.90
Purchase #5	$163.94	12.555%	$184.5227	$184.52	$184.50	$184.50
Purchase #6	$206.82	12.822%	$233.3385	$233.34	$233.35	$233.30
Purchase #7	$179.96	9.231%	$196.5721	$196.57	$196.55	$196.60
7 purchase totals =	$1,200.49		$1,323.2335	$1,323.22	$1,323.20	$1,323.20