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	$139.71	11.853%	$156.2698	$156.27	$156.25	$156.30
Purchase #2	$140.85	8.441%	$152.7391	$152.74	$152.75	$152.70
Purchase #3	$59.99	8.182%	$64.8984	$64.90	$64.90	$64.90
Purchase #4	$209.57	6.527%	$223.2486	$223.25	$223.25	$223.20
Purchase #5	$176.74	7.177%	$189.4246	$189.42	$189.40	$189.40
Purchase #6	$92.89	13.453%	$105.3865	$105.39	$105.40	$105.40
Purchase #7	$67.92	11.316%	$75.6058	$75.61	$75.60	$75.60
7 purchase totals =	$887.67		$967.5728	$967.58	$967.55	$967.50