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	$68.94	4.633%	$72.134	$72.13	$72.15	$72.10
Purchase #2	$204.60	8.141%	$221.2565	$221.26	$221.25	$221.30
Purchase #3	$104.60	12.221%	$117.3832	$117.38	$117.40	$117.40
Purchase #4	$113.87	5.259%	$119.8584	$119.86	$119.85	$119.90
Purchase #5	$23.36	9.457%	$25.5692	$25.57	$25.55	$25.60
Purchase #6	$94.52	11.589%	$105.4739	$105.47	$105.45	$105.50
Purchase #7	$75.48	10.566%	$83.4552	$83.46	$83.45	$83.50
7 purchase totals =	$685.37		$745.1304	$745.13	$745.10	$745.30