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	$48.25	12.466%	$54.2648	$54.26	$54.25	$54.30
Purchase #2	$159.68	4.157%	$166.3179	$166.32	$166.30	$166.30
Purchase #3	$138.47	6.847%	$147.951	$147.95	$147.95	$148.00
Purchase #4	$125.85	12.760%	$141.9085	$141.91	$141.90	$141.90
Purchase #5	$246.82	11.488%	$275.1747	$275.17	$275.15	$275.20
Purchase #6	$246.85	7.872%	$266.282	$266.28	$266.30	$266.30
Purchase #7	$116.33	9.105%	$126.9218	$126.92	$126.90	$126.90
7 purchase totals =	$1,082.25		$1,178.8207	$1,178.81	$1,178.75	$1,178.90