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	$6.84	4.635%	$7.157	$7.16	$7.15	$7.20
Purchase #2	$34.61	8.658%	$37.6065	$37.61	$37.60	$37.60
Purchase #3	$40.81	10.833%	$45.2309	$45.23	$45.25	$45.20
Purchase #4	$150.50	3.789%	$156.2024	$156.20	$156.20	$156.20
Purchase #5	$81.65	12.327%	$91.715	$91.72	$91.70	$91.70
Purchase #6	$200.82	7.405%	$215.6907	$215.69	$215.70	$215.70
Purchase #7	$46.89	8.442%	$50.8485	$50.85	$50.85	$50.80
7 purchase totals =	$562.12		$604.4510	$604.46	$604.45	$604.40