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	$75.51	10.859%	$83.7096	$83.71	$83.70	$83.70
Purchase #2	$111.95	4.104%	$116.5444	$116.54	$116.55	$116.50
Purchase #3	$98.61	3.152%	$101.7182	$101.72	$101.70	$101.70
Purchase #4	$234.28	10.179%	$258.1274	$258.13	$258.15	$258.10
Purchase #5	$84.43	13.256%	$95.622	$95.62	$95.60	$95.60
Purchase #6	$36.67	3.323%	$37.8885	$37.89	$37.90	$37.90
Purchase #7	$239.87	3.519%	$248.311	$248.31	$248.30	$248.30
7 purchase totals =	$881.32		$941.9211	$941.92	$941.90	$941.80