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 $219.62   11.421%   $244.7028   $244.70   $244.70   $244.70  
  Purchase #2 $11.56   7.789%   $12.4604   $12.46   $12.45   $12.50  
  Purchase #3 $212.59   13.380%   $241.0345   $241.03   $241.05   $241.00  
  Purchase #4 $166.77   11.187%   $185.4266   $185.43   $185.45   $185.40  
  Purchase #5 $196.67   12.766%   $221.7769   $221.78   $221.80   $221.80  
  Purchase #6 $170.92   3.701%   $177.2457   $177.25   $177.25   $177.20  
  Purchase #7 $188.78   8.458%   $204.747   $204.75   $204.75   $204.70  
  7 purchase totals = $1,166.91       $1,287.3939   $1,287.40   $1,287.45   $1,287.30