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	$247.27	12.820%	$278.97	$278.97	$278.95	$279.00
Purchase #2	$229.27	5.292%	$241.403	$241.40	$241.40	$241.40
Purchase #3	$54.28	9.822%	$59.6114	$59.61	$59.60	$59.60
Purchase #4	$7.57	3.374%	$7.8254	$7.83	$7.85	$7.80
Purchase #5	$155.56	3.207%	$160.5488	$160.55	$160.55	$160.50
Purchase #6	$151.45	12.591%	$170.5191	$170.52	$170.50	$170.50
Purchase #7	$183.69	11.545%	$204.897	$204.90	$204.90	$204.90
7 purchase totals =	$1,029.09		$1,123.7747	$1,123.78	$1,123.75	$1,123.70