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	$43.84	4.168%	$45.6673	$45.67	$45.65	$45.70
Purchase #2	$164.47	4.700%	$172.2001	$172.20	$172.20	$172.20
Purchase #3	$170.83	8.606%	$185.5316	$185.53	$185.55	$185.50
Purchase #4	$185.62	13.503%	$210.6843	$210.68	$210.70	$210.70
Purchase #5	$54.75	4.662%	$57.3024	$57.30	$57.30	$57.30
Purchase #6	$31.66	3.670%	$32.8219	$32.82	$32.80	$32.80
Purchase #7	$157.39	13.477%	$178.6015	$178.60	$178.60	$178.60
7 purchase totals =	$808.56		$882.8091	$882.80	$882.80	$882.80