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	$21.30	7.321%	$22.8594	$22.86	$22.85	$22.90
Purchase #2	$197.40	8.130%	$213.4486	$213.45	$213.45	$213.40
Purchase #3	$176.66	13.735%	$200.9243	$200.92	$200.90	$200.90
Purchase #4	$98.78	7.706%	$106.392	$106.39	$106.40	$106.40
Purchase #5	$241.74	8.520%	$262.3362	$262.34	$262.35	$262.30
Purchase #6	$87.70	3.241%	$90.5424	$90.54	$90.55	$90.50
Purchase #7	$250.30	7.692%	$269.5531	$269.55	$269.55	$269.60
7 purchase totals =	$1,073.88		$1,166.0560	$1,166.05	$1,166.05	$1,166.00