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	$34.46	9.543%	$37.7485	$37.75	$37.75	$37.70
Purchase #2	$225.76	13.346%	$255.8899	$255.89	$255.90	$255.90
Purchase #3	$192.59	12.656%	$216.9642	$216.96	$216.95	$217.00
Purchase #4	$75.56	8.425%	$81.9259	$81.93	$81.95	$81.90
Purchase #5	$158.64	9.340%	$173.457	$173.46	$173.45	$173.50
Purchase #6	$184.68	13.261%	$209.1704	$209.17	$209.15	$209.20
Purchase #7	$63.54	10.744%	$70.3667	$70.37	$70.35	$70.40
7 purchase totals =	$935.23		$1,045.5226	$1,045.53	$1,045.50	$1,045.60