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	$10.47	9.452%	$11.4596	$11.46	$11.45	$11.50
Purchase #2	$78.57	8.571%	$85.3042	$85.30	$85.30	$85.30
Purchase #3	$156.58	10.139%	$172.4556	$172.46	$172.45	$172.50
Purchase #4	$19.84	8.255%	$21.4778	$21.48	$21.50	$21.50
Purchase #5	$32.74	5.157%	$34.4284	$34.43	$34.45	$34.40
Purchase #6	$135.98	7.115%	$145.655	$145.66	$145.65	$145.70
Purchase #7	$99.95	9.410%	$109.3553	$109.36	$109.35	$109.40
7 purchase totals =	$534.13		$580.1359	$580.15	$580.15	$580.30