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	$41.35	10.583%	$45.7261	$45.73	$45.75	$45.70
Purchase #2	$52.53	7.793%	$56.6237	$56.62	$56.60	$56.60
Purchase #3	$180.87	8.189%	$195.6814	$195.68	$195.70	$195.70
Purchase #4	$177.47	4.506%	$185.4668	$185.47	$185.45	$185.50
Purchase #5	$49.54	12.820%	$55.891	$55.89	$55.90	$55.90
Purchase #6	$60.54	4.384%	$63.1941	$63.19	$63.20	$63.20
Purchase #7	$89.42	10.587%	$98.8869	$98.89	$98.90	$98.90
7 purchase totals =	$651.72		$701.4700	$701.47	$701.50	$701.50