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	$76.65	11.234%	$85.2609	$85.26	$85.25	$85.30
Purchase #2	$231.59	6.777%	$247.2849	$247.28	$247.30	$247.30
Purchase #3	$31.44	3.630%	$32.5813	$32.58	$32.60	$32.60
Purchase #4	$8.36	7.192%	$8.9613	$8.96	$8.95	$9.00
Purchase #5	$67.66	5.698%	$71.5153	$71.52	$71.50	$71.50
Purchase #6	$155.74	11.447%	$173.5676	$173.57	$173.55	$173.60
Purchase #7	$186.92	5.290%	$196.8081	$196.81	$196.80	$196.80
7 purchase totals =	$758.36		$815.9794	$815.98	$815.95	$816.10