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	$201.75	7.459%	$216.7985	$216.80	$216.80	$216.80
Purchase #2	$92.25	9.652%	$101.154	$101.15	$101.15	$101.20
Purchase #3	$188.26	4.492%	$196.7166	$196.72	$196.70	$196.70
Purchase #4	$136.58	10.103%	$150.3787	$150.38	$150.40	$150.40
Purchase #5	$110.92	7.694%	$119.4542	$119.45	$119.45	$119.50
Purchase #6	$155.81	8.339%	$168.803	$168.80	$168.80	$168.80
Purchase #7	$6.97	8.286%	$7.5475	$7.55	$7.55	$7.50
7 purchase totals =	$892.54		$960.8525	$960.85	$960.85	$960.90