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	$199.88	11.451%	$222.7683	$222.77	$222.75	$222.80
Purchase #2	$52.81	12.695%	$59.5142	$59.51	$59.50	$59.50
Purchase #3	$210.96	13.437%	$239.3067	$239.31	$239.30	$239.30
Purchase #4	$183.55	13.330%	$208.0172	$208.02	$208.00	$208.00
Purchase #5	$57.51	11.332%	$64.027	$64.03	$64.05	$64.00
Purchase #6	$198.87	4.393%	$207.6064	$207.61	$207.60	$207.60
Purchase #7	$90.27	11.624%	$100.763	$100.76	$100.75	$100.80
7 purchase totals =	$993.85		$1,102.0028	$1,102.01	$1,101.95	$1,102.00