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 $95.98   11.461%   $106.9803   $106.98   $107.00   $107.00  
  Purchase #2 $249.56   11.133%   $277.3435   $277.34   $277.35   $277.30  
  Purchase #3 $126.69   7.312%   $135.9536   $135.95   $135.95   $136.00  
  Purchase #4 $158.59   12.455%   $178.3424   $178.34   $178.35   $178.30  
  Purchase #5 $183.54   12.739%   $206.9212   $206.92   $206.90   $206.90  
  Purchase #6 $29.59   7.305%   $31.7515   $31.75   $31.75   $31.80  
  Purchase #7 $15.89   7.172%   $17.0296   $17.03   $17.05   $17.00  
  7 purchase totals = $859.84       $954.3221   $954.31   $954.35   $954.30