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	$203.40	8.436%	$220.5588	$220.56	$220.55	$220.60
Purchase #2	$218.45	13.852%	$248.7097	$248.71	$248.70	$248.70
Purchase #3	$22.77	8.258%	$24.6503	$24.65	$24.65	$24.70
Purchase #4	$37.82	13.312%	$42.8546	$42.85	$42.85	$42.90
Purchase #5	$244.89	5.417%	$258.1557	$258.16	$258.15	$258.20
Purchase #6	$78.59	5.295%	$82.7513	$82.75	$82.75	$82.80
Purchase #7	$160.59	9.798%	$176.3246	$176.32	$176.30	$176.30
7 purchase totals =	$966.51		$1,054.0050	$1,054.00	$1,053.95	$1,054.20