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	$88.87	6.531%	$94.6741	$94.67	$94.65	$94.70
Purchase #2	$97.39	3.517%	$100.8152	$100.82	$100.80	$100.80
Purchase #3	$134.62	12.701%	$151.7181	$151.72	$151.70	$151.70
Purchase #4	$193.88	8.761%	$210.8658	$210.87	$210.85	$210.90
Purchase #5	$181.85	5.853%	$192.4937	$192.49	$192.50	$192.50
Purchase #6	$94.95	4.115%	$98.8572	$98.86	$98.85	$98.90
Purchase #7	$93.82	9.830%	$103.0425	$103.04	$103.05	$103.00
7 purchase totals =	$885.38		$952.4666	$952.47	$952.40	$952.50