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	$118.32	7.686%	$127.4141	$127.41	$127.40	$127.40
Purchase #2	$126.86	12.169%	$142.2976	$142.30	$142.30	$142.30
Purchase #3	$55.39	8.196%	$59.9298	$59.93	$59.95	$59.90
Purchase #4	$120.59	3.542%	$124.8613	$124.86	$124.85	$124.90
Purchase #5	$34.54	3.485%	$35.7437	$35.74	$35.75	$35.70
Purchase #6	$212.33	13.691%	$241.4001	$241.40	$241.40	$241.40
Purchase #7	$224.34	4.730%	$234.9513	$234.95	$234.95	$235.00
7 purchase totals =	$892.37		$966.5979	$966.59	$966.60	$966.60