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	$156.42	11.632%	$174.6148	$174.61	$174.60	$174.60
Purchase #2	$161.47	11.788%	$180.5041	$180.50	$180.50	$180.50
Purchase #3	$138.96	13.264%	$157.3917	$157.39	$157.40	$157.40
Purchase #4	$59.66	8.255%	$64.5849	$64.58	$64.60	$64.60
Purchase #5	$233.90	9.144%	$255.2878	$255.29	$255.30	$255.30
Purchase #6	$34.83	6.245%	$37.0051	$37.01	$37.00	$37.00
Purchase #7	$175.83	12.237%	$197.3463	$197.35	$197.35	$197.30
7 purchase totals =	$961.07		$1,066.7347	$1,066.73	$1,066.75	$1,066.70