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 $240.60   8.498%   $261.0462   $261.05   $261.05   $261.00  
  Purchase #2 $227.74   11.702%   $254.3901   $254.39   $254.40   $254.40  
  Purchase #3 $64.28   6.755%   $68.6221   $68.62   $68.60   $68.60  
  Purchase #4 $223.42   7.717%   $240.6613   $240.66   $240.65   $240.70  
  Purchase #5 $188.86   8.843%   $205.5609   $205.56   $205.55   $205.60  
  Purchase #6 $59.46   8.813%   $64.7002   $64.70   $64.70   $64.70  
  Purchase #7 $62.57   7.237%   $67.0982   $67.10   $67.10   $67.10  
  7 purchase totals = $1,066.93       $1,162.0790   $1,162.08   $1,162.05   $1,162.10