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	$6.91	7.245%	$7.4106	$7.41	$7.40	$7.40
Purchase #2	$85.64	4.348%	$89.3636	$89.36	$89.35	$89.40
Purchase #3	$183.91	4.314%	$191.8439	$191.84	$191.85	$191.80
Purchase #4	$22.59	13.873%	$25.7239	$25.72	$25.70	$25.70
Purchase #5	$31.32	11.738%	$34.9963	$35.00	$35.00	$35.00
Purchase #6	$92.25	3.705%	$95.6679	$95.67	$95.65	$95.70
Purchase #7	$108.91	9.726%	$119.5026	$119.50	$119.50	$119.50
7 purchase totals =	$531.53		$564.5088	$564.50	$564.45	$564.50