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	$112.67	13.142%	$127.4771	$127.48	$127.50	$127.50
Purchase #2	$26.85	6.766%	$28.6667	$28.67	$28.65	$28.70
Purchase #3	$217.27	6.855%	$232.1639	$232.16	$232.15	$232.20
Purchase #4	$112.50	6.228%	$119.5065	$119.51	$119.50	$119.50
Purchase #5	$130.75	11.633%	$145.9601	$145.96	$145.95	$146.00
Purchase #6	$241.60	13.263%	$273.6434	$273.64	$273.65	$273.60
Purchase #7	$227.84	5.505%	$240.3826	$240.38	$240.40	$240.40
7 purchase totals =	$1,069.48		$1,167.8003	$1,167.80	$1,167.80	$1,167.90