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	$59.61	10.244%	$65.7164	$65.72	$65.70	$65.70
Purchase #2	$65.81	9.418%	$72.008	$72.01	$72.00	$72.00
Purchase #3	$50.94	8.575%	$55.3081	$55.31	$55.30	$55.30
Purchase #4	$62.32	7.592%	$67.0513	$67.05	$67.05	$67.10
Purchase #5	$7.80	10.308%	$8.604	$8.60	$8.60	$8.60
Purchase #6	$29.93	13.676%	$34.0232	$34.02	$34.00	$34.00
Purchase #7	$130.34	13.558%	$148.0115	$148.01	$148.00	$148.00
7 purchase totals =	$406.75		$450.7225	$450.72	$450.65	$450.70