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	$90.85	12.217%	$101.9491	$101.95	$101.95	$101.90
Purchase #2	$178.69	13.810%	$203.3671	$203.37	$203.35	$203.40
Purchase #3	$154.98	4.222%	$161.5233	$161.52	$161.50	$161.50
Purchase #4	$81.31	13.414%	$92.2169	$92.22	$92.20	$92.20
Purchase #5	$247.81	12.655%	$279.1704	$279.17	$279.15	$279.20
Purchase #6	$150.73	13.562%	$171.172	$171.17	$171.15	$171.20
Purchase #7	$229.75	11.245%	$255.5854	$255.59	$255.60	$255.60
7 purchase totals =	$1,134.12		$1,264.9842	$1,264.99	$1,264.90	$1,265.00