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	$133.42	13.289%	$151.1502	$151.15	$151.15	$151.20
Purchase #2	$212.61	4.861%	$222.945	$222.95	$222.95	$222.90
Purchase #3	$141.35	3.181%	$145.8463	$145.85	$145.85	$145.80
Purchase #4	$119.29	4.182%	$124.2787	$124.28	$124.30	$124.30
Purchase #5	$126.63	8.202%	$137.0162	$137.02	$137.00	$137.00
Purchase #6	$191.70	11.688%	$214.1059	$214.11	$214.10	$214.10
Purchase #7	$136.33	11.850%	$152.4851	$152.49	$152.50	$152.50
7 purchase totals =	$1,061.33		$1,147.8274	$1,147.85	$1,147.85	$1,147.80