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	$215.53	3.668%	$223.4356	$223.44	$223.45	$223.40
Purchase #2	$193.67	4.587%	$202.5536	$202.55	$202.55	$202.60
Purchase #3	$61.55	8.213%	$66.6051	$66.61	$66.60	$66.60
Purchase #4	$84.80	6.811%	$90.5757	$90.58	$90.60	$90.60
Purchase #5	$34.36	3.141%	$35.4392	$35.44	$35.45	$35.40
Purchase #6	$56.91	4.521%	$59.4829	$59.48	$59.50	$59.50
Purchase #7	$102.69	10.565%	$113.5392	$113.54	$113.55	$113.50
7 purchase totals =	$749.51		$791.6313	$791.64	$791.70	$791.60