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	$228.63	10.868%	$253.4775	$253.48	$253.50	$253.50
Purchase #2	$244.37	8.311%	$264.6796	$264.68	$264.70	$264.70
Purchase #3	$98.47	6.482%	$104.8528	$104.85	$104.85	$104.90
Purchase #4	$220.80	11.176%	$245.4766	$245.48	$245.50	$245.50
Purchase #5	$102.32	7.722%	$110.2212	$110.22	$110.20	$110.20
Purchase #6	$67.97	6.557%	$72.4268	$72.43	$72.45	$72.40
Purchase #7	$81.48	4.384%	$85.0521	$85.05	$85.05	$85.10
7 purchase totals =	$1,044.04		$1,136.1866	$1,136.19	$1,136.25	$1,136.30