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	$60.39	6.591%	$64.3703	$64.37	$64.35	$64.40
Purchase #2	$73.69	13.584%	$83.7	$83.70	$83.70	$83.70
Purchase #3	$57.61	11.644%	$64.3181	$64.32	$64.30	$64.30
Purchase #4	$49.94	11.571%	$55.7186	$55.72	$55.70	$55.70
Purchase #5	$182.60	5.480%	$192.6065	$192.61	$192.60	$192.60
Purchase #6	$69.54	13.384%	$78.8472	$78.85	$78.85	$78.80
Purchase #7	$80.40	9.200%	$87.7968	$87.80	$87.80	$87.80
7 purchase totals =	$574.17		$627.3575	$627.37	$627.30	$627.30