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	$130.64	10.416%	$144.2475	$144.25	$144.25	$144.20
Purchase #2	$92.81	7.563%	$99.8292	$99.83	$99.85	$99.80
Purchase #3	$65.62	3.400%	$67.8511	$67.85	$67.85	$67.90
Purchase #4	$248.53	5.197%	$261.4461	$261.45	$261.45	$261.40
Purchase #5	$184.84	8.691%	$200.9044	$200.90	$200.90	$200.90
Purchase #6	$35.35	13.575%	$40.1488	$40.15	$40.15	$40.10
Purchase #7	$137.42	3.700%	$142.5045	$142.50	$142.50	$142.50
7 purchase totals =	$895.21		$956.9316	$956.93	$956.95	$956.80