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	$41.58	10.206%	$45.8237	$45.82	$45.80	$45.80
Purchase #2	$143.95	3.444%	$148.9076	$148.91	$148.90	$148.90
Purchase #3	$70.57	8.301%	$76.428	$76.43	$76.45	$76.40
Purchase #4	$47.80	13.871%	$54.4303	$54.43	$54.45	$54.40
Purchase #5	$142.39	7.829%	$153.5377	$153.54	$153.55	$153.50
Purchase #6	$224.79	3.132%	$231.8304	$231.83	$231.85	$231.80
Purchase #7	$111.60	10.606%	$123.4363	$123.44	$123.45	$123.40
7 purchase totals =	$782.68		$834.3940	$834.40	$834.45	$834.20