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	$176.90	3.162%	$182.4936	$182.49	$182.50	$182.50
Purchase #2	$133.57	13.153%	$151.1385	$151.14	$151.15	$151.10
Purchase #3	$53.59	9.850%	$58.8686	$58.87	$58.85	$58.90
Purchase #4	$34.81	8.792%	$37.8705	$37.87	$37.85	$37.90
Purchase #5	$106.61	13.322%	$120.8126	$120.81	$120.80	$120.80
Purchase #6	$139.90	3.488%	$144.7797	$144.78	$144.80	$144.80
Purchase #7	$230.77	13.167%	$261.1555	$261.16	$261.15	$261.20
7 purchase totals =	$876.15		$957.1190	$957.12	$957.10	$957.20