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 $86.39   8.198%   $93.4723   $93.47   $93.45   $93.50  
  Purchase #2 $241.68   9.168%   $263.8372   $263.84   $263.85   $263.80  
  Purchase #3 $152.28   8.317%   $164.9451   $164.95   $164.95   $164.90  
  Purchase #4 $163.90   8.604%   $178.002   $178.00   $178.00   $178.00  
  Purchase #5 $109.60   8.791%   $119.2349   $119.23   $119.25   $119.20  
  Purchase #6 $127.62   8.600%   $138.5953   $138.60   $138.60   $138.60  
  Purchase #7 $135.81   5.346%   $143.0704   $143.07   $143.05   $143.10  
  7 purchase totals = $1,017.28       $1,101.1572   $1,101.16   $1,101.15   $1,101.10