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 $71.25   7.426%   $76.541   $76.54   $76.55   $76.50  
  Purchase #2 $193.72   9.855%   $212.8111   $212.81   $212.80   $212.80  
  Purchase #3 $164.95   10.618%   $182.4644   $182.46   $182.45   $182.50  
  Purchase #4 $26.54   7.722%   $28.5894   $28.59   $28.60   $28.60  
  Purchase #5 $168.44   10.222%   $185.6579   $185.66   $185.65   $185.70  
  Purchase #6 $137.34   8.359%   $148.8203   $148.82   $148.80   $148.80  
  Purchase #7 $174.44   7.634%   $187.7567   $187.76   $187.75   $187.80  
  7 purchase totals = $936.68       $1,022.6408   $1,022.64   $1,022.60   $1,022.70