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	$187.77	7.284%	$201.4472	$201.45	$201.45	$201.40
Purchase #2	$150.60	7.729%	$162.2399	$162.24	$162.25	$162.20
Purchase #3	$29.60	6.313%	$31.4686	$31.47	$31.45	$31.50
Purchase #4	$33.31	11.509%	$37.1436	$37.14	$37.15	$37.10
Purchase #5	$92.80	6.169%	$98.5248	$98.52	$98.50	$98.50
Purchase #6	$227.89	13.441%	$258.5207	$258.52	$258.50	$258.50
Purchase #7	$218.27	4.869%	$228.8976	$228.90	$228.90	$228.90
7 purchase totals =	$940.24		$1,018.2424	$1,018.24	$1,018.20	$1,018.10