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	$103.99	8.250%	$112.5692	$112.57	$112.55	$112.60
Purchase #2	$238.44	11.801%	$266.5783	$266.58	$266.60	$266.60
Purchase #3	$32.78	9.709%	$35.9626	$35.96	$35.95	$36.00
Purchase #4	$234.91	13.434%	$266.4678	$266.47	$266.45	$266.50
Purchase #5	$176.51	5.821%	$186.7846	$186.78	$186.80	$186.80
Purchase #6	$213.71	4.762%	$223.8869	$223.89	$223.90	$223.90
Purchase #7	$46.50	6.373%	$49.4634	$49.46	$49.45	$49.50
7 purchase totals =	$1,046.84		$1,141.7128	$1,141.71	$1,141.70	$1,141.90