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	$152.85	5.298%	$160.948	$160.95	$160.95	$160.90
Purchase #2	$205.36	8.350%	$222.5076	$222.51	$222.50	$222.50
Purchase #3	$209.46	6.377%	$222.8173	$222.82	$222.80	$222.80
Purchase #4	$148.75	13.292%	$168.5219	$168.52	$168.50	$168.50
Purchase #5	$209.67	7.516%	$225.4288	$225.43	$225.45	$225.40
Purchase #6	$228.85	5.828%	$242.1874	$242.19	$242.20	$242.20
Purchase #7	$230.74	8.846%	$251.1513	$251.15	$251.15	$251.20
7 purchase totals =	$1,385.68		$1,493.5623	$1,493.57	$1,493.55	$1,493.50