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	$196.90	10.241%	$217.0645	$217.06	$217.05	$217.10
Purchase #2	$101.62	9.247%	$111.0168	$111.02	$111.00	$111.00
Purchase #3	$216.78	8.220%	$234.5993	$234.60	$234.60	$234.60
Purchase #4	$204.27	13.137%	$231.1049	$231.10	$231.10	$231.10
Purchase #5	$178.63	10.125%	$196.7163	$196.72	$196.70	$196.70
Purchase #6	$39.87	5.358%	$42.0062	$42.01	$42.00	$42.00
Purchase #7	$218.51	7.293%	$234.4459	$234.45	$234.45	$234.40
7 purchase totals =	$1,156.58		$1,266.9539	$1,266.96	$1,266.90	$1,266.90