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	$63.67	11.652%	$71.0888	$71.09	$71.10	$71.10
Purchase #2	$131.86	8.505%	$143.0747	$143.07	$143.05	$143.10
Purchase #3	$225.70	8.680%	$245.2908	$245.29	$245.30	$245.30
Purchase #4	$125.48	8.689%	$136.383	$136.38	$136.40	$136.40
Purchase #5	$82.94	8.521%	$90.0073	$90.01	$90.00	$90.00
Purchase #6	$173.68	13.389%	$196.934	$196.93	$196.95	$196.90
Purchase #7	$115.79	13.530%	$131.4564	$131.46	$131.45	$131.50
7 purchase totals =	$919.12		$1,014.2350	$1,014.23	$1,014.25	$1,014.30