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	$89.95	5.427%	$94.8316	$94.83	$94.85	$94.80
Purchase #2	$161.38	8.122%	$174.4873	$174.49	$174.50	$174.50
Purchase #3	$175.90	7.656%	$189.3669	$189.37	$189.35	$189.40
Purchase #4	$15.57	11.861%	$17.4168	$17.42	$17.40	$17.40
Purchase #5	$153.73	12.461%	$172.8863	$172.89	$172.90	$172.90
Purchase #6	$137.71	4.186%	$143.4745	$143.47	$143.45	$143.50
Purchase #7	$227.30	8.596%	$246.8387	$246.84	$246.85	$246.80
7 purchase totals =	$961.54		$1,039.3021	$1,039.31	$1,039.30	$1,039.30