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	$137.91	5.518%	$145.5199	$145.52	$145.50	$145.50
Purchase #2	$6.95	6.548%	$7.4051	$7.41	$7.40	$7.40
Purchase #3	$48.55	6.662%	$51.7844	$51.78	$51.80	$51.80
Purchase #4	$43.53	6.397%	$46.3146	$46.31	$46.30	$46.30
Purchase #5	$83.25	3.194%	$85.909	$85.91	$85.90	$85.90
Purchase #6	$102.85	10.593%	$113.7449	$113.74	$113.75	$113.70
Purchase #7	$155.67	4.644%	$162.8993	$162.90	$162.90	$162.90
7 purchase totals =	$578.71		$613.5772	$613.57	$613.55	$613.50