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	$131.52	7.131%	$140.8987	$140.90	$140.90	$140.90
Purchase #2	$170.29	13.303%	$192.9437	$192.94	$192.95	$192.90
Purchase #3	$60.61	9.508%	$66.3728	$66.37	$66.35	$66.40
Purchase #4	$229.56	6.451%	$244.3689	$244.37	$244.35	$244.40
Purchase #5	$53.54	7.345%	$57.4725	$57.47	$57.45	$57.50
Purchase #6	$94.30	9.379%	$103.1444	$103.14	$103.15	$103.10
Purchase #7	$95.47	6.581%	$101.7529	$101.75	$101.75	$101.80
7 purchase totals =	$835.29		$906.9539	$906.94	$906.90	$907.00