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	$113.55	4.437%	$118.5882	$118.59	$118.60	$118.60
Purchase #2	$104.32	8.333%	$113.013	$113.01	$113.00	$113.00
Purchase #3	$36.42	12.283%	$40.8935	$40.89	$40.90	$40.90
Purchase #4	$172.93	5.665%	$182.7265	$182.73	$182.75	$182.70
Purchase #5	$80.68	13.487%	$91.5613	$91.56	$91.55	$91.60
Purchase #6	$33.48	7.323%	$35.9317	$35.93	$35.95	$35.90
Purchase #7	$154.50	6.610%	$164.7125	$164.71	$164.70	$164.70
7 purchase totals =	$695.88		$747.4267	$747.42	$747.45	$747.40