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	$236.83	10.228%	$261.053	$261.05	$261.05	$261.10
Purchase #2	$206.32	12.382%	$231.8665	$231.87	$231.85	$231.90
Purchase #3	$208.53	7.302%	$223.7569	$223.76	$223.75	$223.80
Purchase #4	$122.27	10.377%	$134.958	$134.96	$134.95	$135.00
Purchase #5	$88.54	3.783%	$91.8895	$91.89	$91.90	$91.90
Purchase #6	$78.84	13.432%	$89.4298	$89.43	$89.45	$89.40
Purchase #7	$180.71	10.703%	$200.0514	$200.05	$200.05	$200.10
7 purchase totals =	$1,122.04		$1,233.0051	$1,233.01	$1,233.00	$1,233.20