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	$35.53	6.800%	$37.946	$37.95	$37.95	$37.90
Purchase #2	$13.81	5.675%	$14.5937	$14.59	$14.60	$14.60
Purchase #3	$182.50	9.687%	$200.1788	$200.18	$200.20	$200.20
Purchase #4	$218.88	11.206%	$243.4077	$243.41	$243.40	$243.40
Purchase #5	$120.51	13.663%	$136.9753	$136.98	$137.00	$137.00
Purchase #6	$18.29	6.628%	$19.5023	$19.50	$19.50	$19.50
Purchase #7	$110.60	11.441%	$123.2537	$123.25	$123.25	$123.30
7 purchase totals =	$700.12		$775.8575	$775.86	$775.90	$775.90