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	$105.83	3.343%	$109.3679	$109.37	$109.35	$109.40
Purchase #2	$190.62	9.828%	$209.3541	$209.35	$209.35	$209.40
Purchase #3	$188.97	13.566%	$214.6057	$214.61	$214.60	$214.60
Purchase #4	$76.45	6.157%	$81.157	$81.16	$81.15	$81.20
Purchase #5	$5.59	4.740%	$5.855	$5.86	$5.85	$5.90
Purchase #6	$225.60	12.508%	$253.818	$253.82	$253.80	$253.80
Purchase #7	$99.37	12.117%	$111.4107	$111.41	$111.40	$111.40
7 purchase totals =	$892.43		$985.5684	$985.58	$985.50	$985.70