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	$110.63	7.215%	$118.612	$118.61	$118.60	$118.60
Purchase #2	$173.89	11.531%	$193.9413	$193.94	$193.95	$193.90
Purchase #3	$97.77	11.766%	$109.2736	$109.27	$109.25	$109.30
Purchase #4	$8.90	6.204%	$9.4522	$9.45	$9.45	$9.50
Purchase #5	$124.98	13.632%	$142.0173	$142.02	$142.00	$142.00
Purchase #6	$10.87	6.289%	$11.5536	$11.55	$11.55	$11.60
Purchase #7	$108.42	3.140%	$111.8244	$111.82	$111.80	$111.80
7 purchase totals =	$635.46		$696.6744	$696.66	$696.60	$696.70