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	$172.58	7.473%	$185.4769	$185.48	$185.50	$185.50
Purchase #2	$203.47	13.698%	$231.3413	$231.34	$231.35	$231.30
Purchase #3	$16.27	8.525%	$17.657	$17.66	$17.65	$17.70
Purchase #4	$48.34	9.598%	$52.9797	$52.98	$53.00	$53.00
Purchase #5	$38.31	11.106%	$42.5647	$42.56	$42.55	$42.60
Purchase #6	$72.84	5.462%	$76.8185	$76.82	$76.80	$76.80
Purchase #7	$166.50	8.146%	$180.0631	$180.06	$180.05	$180.10
7 purchase totals =	$718.31		$786.9012	$786.90	$786.90	$787.00