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	$95.36	11.442%	$106.2711	$106.27	$106.25	$106.30
Purchase #2	$122.40	7.109%	$131.1014	$131.10	$131.10	$131.10
Purchase #3	$108.48	4.246%	$113.0861	$113.09	$113.10	$113.10
Purchase #4	$185.92	7.808%	$200.4366	$200.44	$200.45	$200.40
Purchase #5	$112.73	10.272%	$124.3096	$124.31	$124.30	$124.30
Purchase #6	$34.79	13.578%	$39.5138	$39.51	$39.50	$39.50
Purchase #7	$139.95	4.675%	$146.4927	$146.49	$146.50	$146.50
7 purchase totals =	$799.63		$861.2113	$861.21	$861.20	$861.20