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	$34.98	8.525%	$37.962	$37.96	$37.95	$38.00
Purchase #2	$185.88	9.874%	$204.2338	$204.23	$204.25	$204.20
Purchase #3	$145.92	4.286%	$152.1741	$152.17	$152.15	$152.20
Purchase #4	$176.44	7.505%	$189.6818	$189.68	$189.70	$189.70
Purchase #5	$190.93	13.285%	$216.2951	$216.30	$216.30	$216.30
Purchase #6	$31.41	5.539%	$33.1498	$33.15	$33.15	$33.10
Purchase #7	$109.95	12.291%	$123.464	$123.46	$123.45	$123.50
7 purchase totals =	$875.51		$956.9606	$956.95	$956.95	$957.00