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	$14.61	4.587%	$15.2802	$15.28	$15.30	$15.30
Purchase #2	$133.82	13.855%	$152.3608	$152.36	$152.35	$152.40
Purchase #3	$145.83	8.697%	$158.5128	$158.51	$158.50	$158.50
Purchase #4	$134.75	13.485%	$152.921	$152.92	$152.90	$152.90
Purchase #5	$93.93	7.710%	$101.172	$101.17	$101.15	$101.20
Purchase #6	$155.86	8.736%	$169.4759	$169.48	$169.50	$169.50
Purchase #7	$149.57	11.125%	$166.2097	$166.21	$166.20	$166.20
7 purchase totals =	$828.37		$915.9324	$915.93	$915.90	$916.00