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	$131.58	12.724%	$148.3222	$148.32	$148.30	$148.30
Purchase #2	$10.32	12.226%	$11.5817	$11.58	$11.60	$11.60
Purchase #3	$160.28	13.260%	$181.5331	$181.53	$181.55	$181.50
Purchase #4	$110.90	5.112%	$116.5692	$116.57	$116.55	$116.60
Purchase #5	$214.93	13.861%	$244.7214	$244.72	$244.70	$244.70
Purchase #6	$158.25	10.130%	$174.2807	$174.28	$174.30	$174.30
Purchase #7	$188.98	10.540%	$208.8985	$208.90	$208.90	$208.90
7 purchase totals =	$975.24		$1,085.9068	$1,085.90	$1,085.90	$1,085.90