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	$231.99	11.441%	$258.532	$258.53	$258.55	$258.50
Purchase #2	$61.91	7.155%	$66.3397	$66.34	$66.35	$66.30
Purchase #3	$73.52	4.501%	$76.8291	$76.83	$76.85	$76.80
Purchase #4	$155.68	9.103%	$169.8516	$169.85	$169.85	$169.90
Purchase #5	$100.59	3.645%	$104.2565	$104.26	$104.25	$104.30
Purchase #6	$95.73	3.454%	$99.0365	$99.04	$99.05	$99.00
Purchase #7	$38.49	9.146%	$42.0103	$42.01	$42.00	$42.00
7 purchase totals =	$757.91		$816.8557	$816.86	$816.90	$816.80