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	$248.66	13.712%	$282.7563	$282.76	$282.75	$282.80
Purchase #2	$207.58	13.634%	$235.8815	$235.88	$235.90	$235.90
Purchase #3	$131.29	11.826%	$146.8164	$146.82	$146.80	$146.80
Purchase #4	$152.55	9.864%	$167.5975	$167.60	$167.60	$167.60
Purchase #5	$204.55	11.697%	$228.4762	$228.48	$228.50	$228.50
Purchase #6	$49.69	3.369%	$51.3641	$51.36	$51.35	$51.40
Purchase #7	$105.95	4.249%	$110.4518	$110.45	$110.45	$110.50
7 purchase totals =	$1,100.27		$1,223.3438	$1,223.35	$1,223.35	$1,223.50