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	$165.32	4.532%	$172.8123	$172.81	$172.80	$172.80
Purchase #2	$88.46	3.391%	$91.4597	$91.46	$91.45	$91.50
Purchase #3	$78.58	5.577%	$82.9624	$82.96	$82.95	$83.00
Purchase #4	$127.57	12.389%	$143.3746	$143.37	$143.35	$143.40
Purchase #5	$242.39	8.821%	$263.7712	$263.77	$263.75	$263.80
Purchase #6	$89.44	10.504%	$98.8348	$98.83	$98.85	$98.80
Purchase #7	$162.81	10.357%	$179.6722	$179.67	$179.65	$179.70
7 purchase totals =	$954.57		$1,032.8872	$1,032.87	$1,032.80	$1,033.00