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	$109.35	3.667%	$113.3599	$113.36	$113.35	$113.40
Purchase #2	$80.72	3.249%	$83.3426	$83.34	$83.35	$83.30
Purchase #3	$243.62	8.673%	$264.7492	$264.75	$264.75	$264.70
Purchase #4	$143.51	5.283%	$151.0916	$151.09	$151.10	$151.10
Purchase #5	$145.35	11.537%	$162.119	$162.12	$162.10	$162.10
Purchase #6	$145.72	11.244%	$162.1048	$162.10	$162.10	$162.10
Purchase #7	$195.38	10.805%	$216.4908	$216.49	$216.50	$216.50
7 purchase totals =	$1,063.65		$1,153.2579	$1,153.25	$1,153.25	$1,153.20