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	$66.48	7.468%	$71.4447	$71.44	$71.45	$71.40
Purchase #2	$127.89	13.538%	$145.2037	$145.20	$145.20	$145.20
Purchase #3	$163.49	3.447%	$169.1255	$169.13	$169.15	$169.10
Purchase #4	$10.73	8.707%	$11.6643	$11.66	$11.65	$11.70
Purchase #5	$95.47	5.710%	$100.9213	$100.92	$100.90	$100.90
Purchase #6	$224.49	7.103%	$240.4355	$240.44	$240.45	$240.40
Purchase #7	$61.61	9.364%	$67.3792	$67.38	$67.40	$67.40
7 purchase totals =	$750.16		$806.1742	$806.17	$806.20	$806.10