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	$69.30	4.792%	$72.6209	$72.62	$72.60	$72.60
Purchase #2	$140.76	13.292%	$159.4698	$159.47	$159.45	$159.50
Purchase #3	$199.41	4.776%	$208.9338	$208.93	$208.95	$208.90
Purchase #4	$112.90	11.757%	$126.1737	$126.17	$126.15	$126.20
Purchase #5	$235.34	7.685%	$253.4259	$253.43	$253.45	$253.40
Purchase #6	$193.71	12.838%	$218.5785	$218.58	$218.60	$218.60
Purchase #7	$152.28	6.110%	$161.5843	$161.58	$161.60	$161.60
7 purchase totals =	$1,103.70		$1,200.7869	$1,200.78	$1,200.80	$1,200.80