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	$125.70	8.475%	$136.3531	$136.35	$136.35	$136.40
Purchase #2	$61.60	3.197%	$63.5694	$63.57	$63.55	$63.60
Purchase #3	$212.96	4.687%	$222.9414	$222.94	$222.95	$222.90
Purchase #4	$138.89	9.329%	$151.847	$151.85	$151.85	$151.80
Purchase #5	$86.72	5.769%	$91.7229	$91.72	$91.70	$91.70
Purchase #6	$148.67	7.849%	$160.3391	$160.34	$160.35	$160.30
Purchase #7	$54.75	4.414%	$57.1667	$57.17	$57.15	$57.20
7 purchase totals =	$829.29		$883.9396	$883.94	$883.90	$883.90