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	$102.27	9.134%	$111.6113	$111.61	$111.60	$111.60
Purchase #2	$34.41	3.734%	$35.6949	$35.69	$35.70	$35.70
Purchase #3	$176.86	5.614%	$186.7889	$186.79	$186.80	$186.80
Purchase #4	$80.26	11.648%	$89.6087	$89.61	$89.60	$89.60
Purchase #5	$190.96	8.838%	$207.837	$207.84	$207.85	$207.80
Purchase #6	$21.33	3.824%	$22.1457	$22.15	$22.15	$22.10
Purchase #7	$18.66	4.736%	$19.5437	$19.54	$19.55	$19.50
7 purchase totals =	$624.75		$673.2302	$673.23	$673.25	$673.10