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	$136.92	8.418%	$148.4459	$148.45	$148.45	$148.40
Purchase #2	$70.86	3.271%	$73.1778	$73.18	$73.20	$73.20
Purchase #3	$37.32	3.311%	$38.5557	$38.56	$38.55	$38.60
Purchase #4	$63.55	13.554%	$72.1636	$72.16	$72.15	$72.20
Purchase #5	$220.79	11.576%	$246.3487	$246.35	$246.35	$246.30
Purchase #6	$151.48	11.276%	$168.5609	$168.56	$168.55	$168.60
Purchase #7	$35.67	5.365%	$37.5837	$37.58	$37.60	$37.60
7 purchase totals =	$716.59		$784.8363	$784.84	$784.85	$784.90