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	$162.30	5.103%	$170.5822	$170.58	$170.60	$170.60
Purchase #2	$188.62	11.659%	$210.6112	$210.61	$210.60	$210.60
Purchase #3	$88.39	3.132%	$91.1584	$91.16	$91.15	$91.20
Purchase #4	$138.68	6.150%	$147.2088	$147.21	$147.20	$147.20
Purchase #5	$34.78	7.538%	$37.4017	$37.40	$37.40	$37.40
Purchase #6	$48.95	11.686%	$54.6703	$54.67	$54.65	$54.70
Purchase #7	$34.96	8.380%	$37.8896	$37.89	$37.90	$37.90
7 purchase totals =	$696.68		$749.5222	$749.52	$749.50	$749.60