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 $88.38   8.576%   $95.9595   $95.96   $95.95   $96.00  
  Purchase #2 $206.56   4.121%   $215.0723   $215.07   $215.05   $215.10  
  Purchase #3 $64.99   13.417%   $73.7097   $73.71   $73.70   $73.70  
  Purchase #4 $135.85   10.214%   $149.7257   $149.73   $149.75   $149.70  
  Purchase #5 $166.85   5.153%   $175.4478   $175.45   $175.45   $175.40  
  Purchase #6 $80.91   11.463%   $90.1847   $90.18   $90.20   $90.20  
  Purchase #7 $197.80   9.691%   $216.9688   $216.97   $216.95   $217.00  
  7 purchase totals = $941.34       $1,017.0685   $1,017.07   $1,017.05   $1,017.10