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	$199.29	10.300%	$219.8169	$219.82	$219.80	$219.80
Purchase #2	$92.80	7.545%	$99.8018	$99.80	$99.80	$99.80
Purchase #3	$105.58	8.350%	$114.3959	$114.40	$114.40	$114.40
Purchase #4	$78.70	9.209%	$85.9475	$85.95	$85.95	$85.90
Purchase #5	$49.63	13.848%	$56.5028	$56.50	$56.50	$56.50
Purchase #6	$121.97	5.152%	$128.2539	$128.25	$128.25	$128.30
Purchase #7	$214.83	10.248%	$236.8458	$236.85	$236.85	$236.80
7 purchase totals =	$862.80		$941.5646	$941.57	$941.55	$941.50