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	$119.26	11.551%	$133.0357	$133.04	$133.05	$133.00
Purchase #2	$129.52	11.457%	$144.3591	$144.36	$144.35	$144.40
Purchase #3	$83.33	10.146%	$91.7847	$91.78	$91.80	$91.80
Purchase #4	$136.69	6.439%	$145.4915	$145.49	$145.50	$145.50
Purchase #5	$221.53	10.296%	$244.3387	$244.34	$244.35	$244.30
Purchase #6	$6.45	13.485%	$7.3198	$7.32	$7.30	$7.30
Purchase #7	$28.51	13.334%	$32.3115	$32.31	$32.30	$32.30
7 purchase totals =	$725.29		$798.6410	$798.64	$798.65	$798.60