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	$178.54	11.466%	$199.0114	$199.01	$199.00	$199.00
Purchase #2	$75.49	13.284%	$85.5181	$85.52	$85.50	$85.50
Purchase #3	$133.38	13.693%	$151.6437	$151.64	$151.65	$151.60
Purchase #4	$189.64	11.371%	$211.204	$211.20	$211.20	$211.20
Purchase #5	$149.47	12.321%	$167.8862	$167.89	$167.90	$167.90
Purchase #6	$185.32	3.249%	$191.341	$191.34	$191.35	$191.30
Purchase #7	$234.98	9.793%	$257.9916	$257.99	$258.00	$258.00
7 purchase totals =	$1,146.82		$1,264.5960	$1,264.59	$1,264.60	$1,264.50