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	$106.86	4.417%	$111.58	$111.58	$111.60	$111.60
Purchase #2	$216.58	11.578%	$241.6556	$241.66	$241.65	$241.70
Purchase #3	$109.50	3.819%	$113.6818	$113.68	$113.70	$113.70
Purchase #4	$142.62	11.574%	$159.1268	$159.13	$159.15	$159.10
Purchase #5	$32.80	6.868%	$35.0527	$35.05	$35.05	$35.10
Purchase #6	$108.61	5.746%	$114.8507	$114.85	$114.85	$114.90
Purchase #7	$58.40	5.745%	$61.7551	$61.76	$61.75	$61.80
7 purchase totals =	$775.37		$837.7027	$837.71	$837.75	$837.90