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	$205.34	6.386%	$218.453	$218.45	$218.45	$218.50
Purchase #2	$90.82	3.729%	$94.2067	$94.21	$94.20	$94.20
Purchase #3	$44.54	9.155%	$48.6176	$48.62	$48.60	$48.60
Purchase #4	$177.67	10.647%	$196.5865	$196.59	$196.60	$196.60
Purchase #5	$57.85	10.124%	$63.7067	$63.71	$63.70	$63.70
Purchase #6	$21.64	13.196%	$24.4956	$24.50	$24.50	$24.50
Purchase #7	$44.53	6.321%	$47.3447	$47.34	$47.35	$47.30
7 purchase totals =	$642.39		$693.4108	$693.42	$693.40	$693.40