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	$167.57	11.754%	$187.2662	$187.27	$187.25	$187.30
Purchase #2	$171.38	3.252%	$176.9533	$176.95	$176.95	$177.00
Purchase #3	$34.90	6.863%	$37.2952	$37.30	$37.30	$37.30
Purchase #4	$137.41	6.580%	$146.4516	$146.45	$146.45	$146.50
Purchase #5	$244.39	12.677%	$275.3713	$275.37	$275.35	$275.40
Purchase #6	$73.41	7.253%	$78.7344	$78.73	$78.75	$78.70
Purchase #7	$64.87	12.114%	$72.7284	$72.73	$72.75	$72.70
7 purchase totals =	$893.93		$974.8004	$974.80	$974.80	$974.90