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	$169.27	3.325%	$174.8982	$174.90	$174.90	$174.90
Purchase #2	$177.96	6.712%	$189.9047	$189.90	$189.90	$189.90
Purchase #3	$132.39	11.373%	$147.4467	$147.45	$147.45	$147.40
Purchase #4	$85.57	7.852%	$92.289	$92.29	$92.30	$92.30
Purchase #5	$157.86	8.471%	$171.2323	$171.23	$171.25	$171.20
Purchase #6	$224.35	3.391%	$231.9577	$231.96	$231.95	$232.00
Purchase #7	$199.42	4.555%	$208.5036	$208.50	$208.50	$208.50
7 purchase totals =	$1,146.82		$1,216.2322	$1,216.23	$1,216.25	$1,216.20