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	$195.93	10.549%	$216.5987	$216.60	$216.60	$216.60
Purchase #2	$147.55	13.717%	$167.7894	$167.79	$167.80	$167.80
Purchase #3	$171.38	10.736%	$189.7794	$189.78	$189.80	$189.80
Purchase #4	$57.27	4.404%	$59.7922	$59.79	$59.80	$59.80
Purchase #5	$52.61	9.814%	$57.7731	$57.77	$57.75	$57.80
Purchase #6	$72.27	11.472%	$80.5608	$80.56	$80.55	$80.60
Purchase #7	$57.80	9.117%	$63.0696	$63.07	$63.05	$63.10
7 purchase totals =	$754.81		$835.3632	$835.36	$835.35	$835.50