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	$139.77	12.503%	$157.2454	$157.25	$157.25	$157.20
Purchase #2	$216.41	4.275%	$225.6615	$225.66	$225.65	$225.70
Purchase #3	$139.38	5.274%	$146.7309	$146.73	$146.75	$146.70
Purchase #4	$104.53	9.465%	$114.4238	$114.42	$114.40	$114.40
Purchase #5	$237.52	7.630%	$255.6428	$255.64	$255.65	$255.60
Purchase #6	$58.74	6.585%	$62.608	$62.61	$62.60	$62.60
Purchase #7	$187.85	6.734%	$200.4998	$200.50	$200.50	$200.50
7 purchase totals =	$1,084.20		$1,162.8122	$1,162.81	$1,162.80	$1,162.70