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	$238.57	10.127%	$262.73	$262.73	$262.75	$262.70
Purchase #2	$182.95	12.317%	$205.484	$205.48	$205.50	$205.50
Purchase #3	$20.97	3.319%	$21.666	$21.67	$21.65	$21.70
Purchase #4	$234.59	6.285%	$249.334	$249.33	$249.35	$249.30
Purchase #5	$102.53	5.546%	$108.2163	$108.22	$108.20	$108.20
Purchase #6	$90.95	8.138%	$98.3515	$98.35	$98.35	$98.40
Purchase #7	$149.41	3.229%	$154.2344	$154.23	$154.25	$154.20
7 purchase totals =	$1,019.97		$1,100.0162	$1,100.01	$1,100.05	$1,100.00