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	$86.39	12.125%	$96.8648	$96.86	$96.85	$96.90
Purchase #2	$212.55	13.671%	$241.6077	$241.61	$241.60	$241.60
Purchase #3	$195.34	13.374%	$221.4648	$221.46	$221.45	$221.50
Purchase #4	$24.85	9.144%	$27.1223	$27.12	$27.10	$27.10
Purchase #5	$232.68	3.660%	$241.1961	$241.20	$241.20	$241.20
Purchase #6	$121.55	5.209%	$127.8815	$127.88	$127.90	$127.90
Purchase #7	$77.31	8.397%	$83.8017	$83.80	$83.80	$83.80
7 purchase totals =	$950.67		$1,039.9389	$1,039.93	$1,039.90	$1,040.00