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	$52.65	12.730%	$59.3523	$59.35	$59.35	$59.40
Purchase #2	$23.38	7.600%	$25.1569	$25.16	$25.15	$25.20
Purchase #3	$219.92	7.572%	$236.5723	$236.57	$236.55	$236.60
Purchase #4	$250.30	9.571%	$274.2562	$274.26	$274.25	$274.30
Purchase #5	$152.79	8.266%	$165.4196	$165.42	$165.40	$165.40
Purchase #6	$100.52	12.314%	$112.898	$112.90	$112.90	$112.90
Purchase #7	$50.94	8.660%	$55.3514	$55.35	$55.35	$55.40
7 purchase totals =	$850.50		$929.0067	$929.01	$928.95	$929.20