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	$233.30	6.841%	$249.2601	$249.26	$249.25	$249.30
Purchase #2	$104.50	6.326%	$111.1107	$111.11	$111.10	$111.10
Purchase #3	$58.61	13.198%	$66.3453	$66.35	$66.35	$66.30
Purchase #4	$61.90	11.725%	$69.1578	$69.16	$69.15	$69.20
Purchase #5	$104.87	6.453%	$111.6373	$111.64	$111.65	$111.60
Purchase #6	$24.42	8.750%	$26.5568	$26.56	$26.55	$26.60
Purchase #7	$140.77	8.643%	$152.9368	$152.94	$152.95	$152.90
7 purchase totals =	$728.37		$787.0048	$787.02	$787.00	$787.00