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	$153.41	12.714%	$172.9145	$172.91	$172.90	$172.90
Purchase #2	$38.54	9.529%	$42.2125	$42.21	$42.20	$42.20
Purchase #3	$41.95	3.406%	$43.3788	$43.38	$43.40	$43.40
Purchase #4	$29.89	5.431%	$31.5133	$31.51	$31.50	$31.50
Purchase #5	$234.61	11.790%	$262.2705	$262.27	$262.25	$262.30
Purchase #6	$7.47	11.772%	$8.3494	$8.35	$8.35	$8.30
Purchase #7	$139.79	10.525%	$154.5029	$154.50	$154.50	$154.50
7 purchase totals =	$645.66		$715.1419	$715.13	$715.10	$715.10