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	$31.73	3.253%	$32.7622	$32.76	$32.75	$32.80
Purchase #2	$38.71	4.724%	$40.5387	$40.54	$40.55	$40.50
Purchase #3	$79.76	13.837%	$90.7964	$90.80	$90.80	$90.80
Purchase #4	$34.67	9.255%	$37.8787	$37.88	$37.90	$37.90
Purchase #5	$163.74	13.686%	$186.1495	$186.15	$186.15	$186.10
Purchase #6	$92.55	9.801%	$101.6208	$101.62	$101.60	$101.60
Purchase #7	$211.58	5.443%	$223.0963	$223.10	$223.10	$223.10
7 purchase totals =	$652.74		$712.8426	$712.85	$712.85	$712.80