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	$40.51	12.297%	$45.4915	$45.49	$45.50	$45.50
Purchase #2	$35.82	5.120%	$37.654	$37.65	$37.65	$37.70
Purchase #3	$102.94	11.135%	$114.4024	$114.40	$114.40	$114.40
Purchase #4	$122.78	11.817%	$137.2889	$137.29	$137.30	$137.30
Purchase #5	$87.56	3.221%	$90.3803	$90.38	$90.40	$90.40
Purchase #6	$7.62	5.187%	$8.0152	$8.02	$8.00	$8.00
Purchase #7	$153.64	12.486%	$172.8235	$172.82	$172.80	$172.80
7 purchase totals =	$550.87		$606.0558	$606.05	$606.05	$606.10