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	$105.54	5.433%	$111.274	$111.27	$111.25	$111.30
Purchase #2	$57.72	9.797%	$63.3748	$63.37	$63.35	$63.40
Purchase #3	$13.95	5.431%	$14.7076	$14.71	$14.70	$14.70
Purchase #4	$198.84	7.486%	$213.7252	$213.73	$213.75	$213.70
Purchase #5	$232.61	11.830%	$260.1278	$260.13	$260.15	$260.10
Purchase #6	$36.34	4.750%	$38.0662	$38.07	$38.05	$38.10
Purchase #7	$64.90	4.181%	$67.6135	$67.61	$67.60	$67.60
7 purchase totals =	$709.90		$768.8891	$768.89	$768.85	$768.90