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	$85.97	4.307%	$89.6727	$89.67	$89.65	$89.70
Purchase #2	$215.57	6.162%	$228.8534	$228.85	$228.85	$228.90
Purchase #3	$227.77	4.821%	$238.7508	$238.75	$238.75	$238.80
Purchase #4	$49.60	8.321%	$53.7272	$53.73	$53.75	$53.70
Purchase #5	$187.89	13.578%	$213.4017	$213.40	$213.40	$213.40
Purchase #6	$200.37	11.807%	$224.0277	$224.03	$224.05	$224.00
Purchase #7	$61.48	6.459%	$65.451	$65.45	$65.45	$65.50
7 purchase totals =	$1,028.65		$1,113.8845	$1,113.88	$1,113.90	$1,114.00