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 $85.79   10.718%   $94.985   $94.99   $95.00   $95.00  
  Purchase #2 $242.59   5.367%   $255.6098   $255.61   $255.60   $255.60  
  Purchase #3 $175.72   3.677%   $182.1812   $182.18   $182.20   $182.20  
  Purchase #4 $18.64   8.578%   $20.2389   $20.24   $20.25   $20.20  
  Purchase #5 $140.81   8.112%   $152.2325   $152.23   $152.25   $152.20  
  Purchase #6 $10.84   9.656%   $11.8867   $11.89   $11.90   $11.90  
  Purchase #7 $178.64   11.714%   $199.5659   $199.57   $199.55   $199.60  
  7 purchase totals = $853.03       $916.7000   $916.71   $916.75   $916.70