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	$37.89	10.396%	$41.829	$41.83	$41.85	$41.80
Purchase #2	$186.34	11.545%	$207.853	$207.85	$207.85	$207.90
Purchase #3	$143.90	13.252%	$162.9696	$162.97	$162.95	$163.00
Purchase #4	$87.83	9.212%	$95.9209	$95.92	$95.90	$95.90
Purchase #5	$205.82	13.287%	$233.1673	$233.17	$233.15	$233.20
Purchase #6	$66.40	7.272%	$71.2286	$71.23	$71.25	$71.20
Purchase #7	$69.42	3.530%	$71.8705	$71.87	$71.85	$71.90
7 purchase totals =	$797.60		$884.8389	$884.84	$884.80	$884.90