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	$237.25	7.759%	$255.6582	$255.66	$255.65	$255.70
Purchase #2	$149.72	6.308%	$159.1643	$159.16	$159.15	$159.20
Purchase #3	$159.90	13.494%	$181.4769	$181.48	$181.50	$181.50
Purchase #4	$96.55	6.107%	$102.4463	$102.45	$102.45	$102.40
Purchase #5	$65.75	10.321%	$72.5361	$72.54	$72.55	$72.50
Purchase #6	$72.67	6.811%	$77.6196	$77.62	$77.60	$77.60
Purchase #7	$152.59	3.438%	$157.836	$157.84	$157.85	$157.80
7 purchase totals =	$934.43		$1,006.7374	$1,006.75	$1,006.75	$1,006.70