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	$85.73	12.514%	$96.4583	$96.46	$96.45	$96.50
Purchase #2	$157.57	8.849%	$171.5134	$171.51	$171.50	$171.50
Purchase #3	$38.97	5.562%	$41.1375	$41.14	$41.15	$41.10
Purchase #4	$96.41	8.685%	$104.7832	$104.78	$104.80	$104.80
Purchase #5	$20.38	6.105%	$21.6242	$21.62	$21.60	$21.60
Purchase #6	$124.32	5.598%	$131.2794	$131.28	$131.30	$131.30
Purchase #7	$114.33	13.596%	$129.8743	$129.87	$129.85	$129.90
7 purchase totals =	$637.71		$696.6703	$696.66	$696.65	$696.70