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	$214.28	4.354%	$223.6098	$223.61	$223.60	$223.60
Purchase #2	$225.62	8.410%	$244.5946	$244.59	$244.60	$244.60
Purchase #3	$159.42	7.631%	$171.5853	$171.59	$171.60	$171.60
Purchase #4	$52.46	10.828%	$58.1404	$58.14	$58.15	$58.10
Purchase #5	$28.70	3.778%	$29.7843	$29.78	$29.80	$29.80
Purchase #6	$199.71	5.761%	$211.2153	$211.22	$211.20	$211.20
Purchase #7	$178.69	12.302%	$200.6724	$200.67	$200.65	$200.70
7 purchase totals =	$1,058.88		$1,139.6021	$1,139.60	$1,139.60	$1,139.60