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	$125.46	7.348%	$134.6788	$134.68	$134.70	$134.70
Purchase #2	$134.29	6.853%	$143.4929	$143.49	$143.50	$143.50
Purchase #3	$237.58	9.830%	$260.9341	$260.93	$260.95	$260.90
Purchase #4	$81.33	12.713%	$91.6695	$91.67	$91.65	$91.70
Purchase #5	$38.43	11.407%	$42.8137	$42.81	$42.80	$42.80
Purchase #6	$81.60	11.404%	$90.9057	$90.91	$90.90	$90.90
Purchase #7	$200.36	9.223%	$218.8392	$218.84	$218.85	$218.80
7 purchase totals =	$899.05		$983.3339	$983.33	$983.35	$983.30