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	$83.45	13.430%	$94.6573	$94.66	$94.65	$94.70
Purchase #2	$159.68	8.611%	$173.43	$173.43	$173.45	$173.40
Purchase #3	$203.35	5.846%	$215.2378	$215.24	$215.25	$215.20
Purchase #4	$82.58	11.449%	$92.0346	$92.03	$92.05	$92.00
Purchase #5	$173.82	13.131%	$196.6443	$196.64	$196.65	$196.60
Purchase #6	$167.47	8.610%	$181.8892	$181.89	$181.90	$181.90
Purchase #7	$11.78	4.639%	$12.3265	$12.33	$12.35	$12.30
7 purchase totals =	$882.13		$966.2197	$966.22	$966.30	$966.10