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	$167.92	13.232%	$190.1392	$190.14	$190.15	$190.10
Purchase #2	$219.60	11.558%	$244.9814	$244.98	$245.00	$245.00
Purchase #3	$92.43	8.538%	$100.3217	$100.32	$100.30	$100.30
Purchase #4	$74.53	7.210%	$79.9036	$79.90	$79.90	$79.90
Purchase #5	$98.74	3.469%	$102.1653	$102.17	$102.15	$102.20
Purchase #6	$12.32	11.691%	$13.7603	$13.76	$13.75	$13.80
Purchase #7	$156.71	10.700%	$173.478	$173.48	$173.50	$173.50
7 purchase totals =	$822.25		$904.7495	$904.75	$904.75	$904.80