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	$111.62	11.576%	$124.5411	$124.54	$124.55	$124.50
Purchase #2	$6.45	10.377%	$7.1193	$7.12	$7.10	$7.10
Purchase #3	$163.33	5.610%	$172.4928	$172.49	$172.50	$172.50
Purchase #4	$232.37	3.132%	$239.6478	$239.65	$239.65	$239.60
Purchase #5	$207.31	12.504%	$233.232	$233.23	$233.25	$233.20
Purchase #6	$58.51	4.705%	$61.2629	$61.26	$61.25	$61.30
Purchase #7	$123.39	6.664%	$131.6127	$131.61	$131.60	$131.60
7 purchase totals =	$902.98		$969.9086	$969.90	$969.90	$969.80