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	$83.61	12.461%	$94.0286	$94.03	$94.05	$94.00
Purchase #2	$76.55	11.647%	$85.4658	$85.47	$85.45	$85.50
Purchase #3	$57.71	8.468%	$62.5969	$62.60	$62.60	$62.60
Purchase #4	$103.94	8.530%	$112.8061	$112.81	$112.80	$112.80
Purchase #5	$74.96	5.873%	$79.3624	$79.36	$79.35	$79.40
Purchase #6	$119.98	9.743%	$131.6697	$131.67	$131.65	$131.70
Purchase #7	$90.96	10.192%	$100.2306	$100.23	$100.25	$100.20
7 purchase totals =	$607.71		$666.1601	$666.17	$666.15	$666.20