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 $58.79   6.581%   $62.659   $62.66   $62.65   $62.70  
  Purchase #2 $206.62   3.523%   $213.8992   $213.90   $213.90   $213.90  
  Purchase #3 $24.81   13.477%   $28.1536   $28.15   $28.15   $28.20  
  Purchase #4 $29.60   10.636%   $32.7483   $32.75   $32.75   $32.70  
  Purchase #5 $224.68   7.691%   $241.9601   $241.96   $241.95   $242.00  
  Purchase #6 $94.40   5.598%   $99.6845   $99.68   $99.70   $99.70  
  Purchase #7 $47.29   9.608%   $51.8336   $51.83   $51.85   $51.80  
  7 purchase totals = $686.19       $730.9383   $730.93   $730.95   $731.00