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	$174.69	13.480%	$198.2382	$198.24	$198.25	$198.20
Purchase #2	$239.34	9.246%	$261.4694	$261.47	$261.45	$261.50
Purchase #3	$148.29	9.824%	$162.858	$162.86	$162.85	$162.90
Purchase #4	$145.96	7.440%	$156.8194	$156.82	$156.80	$156.80
Purchase #5	$166.93	11.122%	$185.496	$185.50	$185.50	$185.50
Purchase #6	$35.89	5.845%	$37.9878	$37.99	$38.00	$38.00
Purchase #7	$29.88	3.791%	$31.0128	$31.01	$31.00	$31.00
7 purchase totals =	$940.98		$1,033.8816	$1,033.89	$1,033.85	$1,033.90