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	$168.69	7.241%	$180.9048	$180.90	$180.90	$180.90
Purchase #2	$113.47	5.111%	$119.2695	$119.27	$119.25	$119.30
Purchase #3	$25.93	13.282%	$29.374	$29.37	$29.35	$29.40
Purchase #4	$106.48	9.239%	$116.3177	$116.32	$116.30	$116.30
Purchase #5	$37.53	8.666%	$40.7823	$40.78	$40.80	$40.80
Purchase #6	$49.90	3.562%	$51.6774	$51.68	$51.70	$51.70
Purchase #7	$51.96	13.826%	$59.144	$59.14	$59.15	$59.10
7 purchase totals =	$553.96		$597.4697	$597.46	$597.45	$597.50