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 $83.57   13.590%   $94.9272   $94.93   $94.95   $94.90  
  Purchase #2 $245.48   7.236%   $263.2429   $263.24   $263.25   $263.20  
  Purchase #3 $156.28   7.461%   $167.9401   $167.94   $167.95   $167.90  
  Purchase #4 $52.28   8.861%   $56.9125   $56.91   $56.90   $56.90  
  Purchase #5 $204.53   5.641%   $216.0675   $216.07   $216.05   $216.10  
  Purchase #6 $218.87   11.513%   $244.0685   $244.07   $244.05   $244.10  
  Purchase #7 $58.75   6.637%   $62.6492   $62.65   $62.65   $62.60  
  7 purchase totals = $1,019.76       $1,105.8079   $1,105.81   $1,105.80   $1,105.70