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 $87.57   7.311%   $93.9722   $93.97   $93.95   $94.00  
  Purchase #2 $204.84   12.604%   $230.658   $230.66   $230.65   $230.70  
  Purchase #3 $112.82   4.873%   $118.3177   $118.32   $118.30   $118.30  
  Purchase #4 $99.79   4.383%   $104.1638   $104.16   $104.15   $104.20  
  Purchase #5 $64.33   12.458%   $72.3442   $72.34   $72.35   $72.30  
  Purchase #6 $218.98   6.814%   $233.9013   $233.90   $233.90   $233.90  
  Purchase #7 $149.74   5.346%   $157.7451   $157.75   $157.75   $157.70  
  7 purchase totals = $938.07       $1,011.1023   $1,011.10   $1,011.05   $1,011.10