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 $207.95   9.336%   $227.3642   $227.36   $227.35   $227.40  
  Purchase #2 $24.28   5.202%   $25.543   $25.54   $25.55   $25.50  
  Purchase #3 $250.31   6.215%   $265.8668   $265.87   $265.85   $265.90  
  Purchase #4 $140.68   8.525%   $152.673   $152.67   $152.65   $152.70  
  Purchase #5 $69.87   8.224%   $75.6161   $75.62   $75.60   $75.60  
  Purchase #6 $235.43   9.408%   $257.5793   $257.58   $257.60   $257.60  
  Purchase #7 $184.92   9.397%   $202.2969   $202.30   $202.30   $202.30  
  7 purchase totals = $1,113.44       $1,206.9393   $1,206.94   $1,206.90   $1,207.00