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	$142.29	4.514%	$148.713	$148.71	$148.70	$148.70
Purchase #2	$106.97	9.282%	$116.899	$116.90	$116.90	$116.90
Purchase #3	$61.37	9.622%	$67.275	$67.28	$67.30	$67.30
Purchase #4	$94.60	7.640%	$101.8274	$101.83	$101.85	$101.80
Purchase #5	$216.72	13.724%	$246.4627	$246.46	$246.45	$246.50
Purchase #6	$97.75	13.692%	$111.1339	$111.13	$111.15	$111.10
Purchase #7	$25.85	10.858%	$28.6568	$28.66	$28.65	$28.70
7 purchase totals =	$745.55		$820.9678	$820.97	$821.00	$821.00