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	$174.83	8.636%	$189.9283	$189.93	$189.95	$189.90
Purchase #2	$137.86	10.581%	$152.447	$152.45	$152.45	$152.40
Purchase #3	$155.42	3.219%	$160.423	$160.42	$160.40	$160.40
Purchase #4	$25.65	9.200%	$28.0098	$28.01	$28.00	$28.00
Purchase #5	$245.31	11.161%	$272.689	$272.69	$272.70	$272.70
Purchase #6	$227.39	12.443%	$255.6841	$255.68	$255.70	$255.70
Purchase #7	$14.93	3.668%	$15.4776	$15.48	$15.50	$15.50
7 purchase totals =	$981.39		$1,074.6588	$1,074.66	$1,074.70	$1,074.60