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	$169.53	3.515%	$175.489	$175.49	$175.50	$175.50
Purchase #2	$100.73	3.134%	$103.8869	$103.89	$103.90	$103.90
Purchase #3	$41.54	10.268%	$45.8053	$45.81	$45.80	$45.80
Purchase #4	$52.68	12.341%	$59.1812	$59.18	$59.20	$59.20
Purchase #5	$12.40	3.691%	$12.8577	$12.86	$12.85	$12.90
Purchase #6	$21.48	10.611%	$23.7592	$23.76	$23.75	$23.80
Purchase #7	$144.38	4.464%	$150.8251	$150.83	$150.85	$150.80
7 purchase totals =	$542.74		$571.8044	$571.82	$571.85	$571.90