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	$205.89	10.331%	$227.1605	$227.16	$227.15	$227.20
Purchase #2	$43.57	7.566%	$46.8665	$46.87	$46.85	$46.90
Purchase #3	$107.71	3.179%	$111.1341	$111.13	$111.15	$111.10
Purchase #4	$247.39	9.201%	$270.1524	$270.15	$270.15	$270.20
Purchase #5	$113.80	5.763%	$120.3583	$120.36	$120.35	$120.40
Purchase #6	$67.52	5.417%	$71.1776	$71.18	$71.20	$71.20
Purchase #7	$73.95	11.377%	$82.3633	$82.36	$82.35	$82.40
7 purchase totals =	$859.83		$929.2127	$929.21	$929.20	$929.40