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	$209.30	11.719%	$233.8279	$233.83	$233.85	$233.80
Purchase #2	$25.38	8.309%	$27.4888	$27.49	$27.50	$27.50
Purchase #3	$79.25	5.103%	$83.2941	$83.29	$83.30	$83.30
Purchase #4	$71.81	5.167%	$75.5204	$75.52	$75.50	$75.50
Purchase #5	$49.79	8.341%	$53.943	$53.94	$53.95	$53.90
Purchase #6	$72.93	13.140%	$82.513	$82.51	$82.50	$82.50
Purchase #7	$241.42	11.253%	$268.587	$268.59	$268.60	$268.60
7 purchase totals =	$749.88		$825.1742	$825.17	$825.20	$825.10