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	$120.52	13.187%	$136.413	$136.41	$136.40	$136.40
Purchase #2	$87.32	8.804%	$95.0077	$95.01	$95.00	$95.00
Purchase #3	$184.35	10.309%	$203.3546	$203.35	$203.35	$203.40
Purchase #4	$19.25	3.319%	$19.8889	$19.89	$19.90	$19.90
Purchase #5	$123.56	11.340%	$137.5717	$137.57	$137.55	$137.60
Purchase #6	$166.97	3.800%	$173.3149	$173.31	$173.30	$173.30
Purchase #7	$231.80	10.658%	$256.5052	$256.51	$256.50	$256.50
7 purchase totals =	$933.77		$1,022.0560	$1,022.05	$1,022.00	$1,022.10