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 $61.78   12.824%   $69.7027   $69.70   $69.70   $69.70  
  Purchase #2 $237.39   10.392%   $262.0596   $262.06   $262.05   $262.10  
  Purchase #3 $43.88   6.132%   $46.5707   $46.57   $46.55   $46.60  
  Purchase #4 $223.55   7.628%   $240.6024   $240.60   $240.60   $240.60  
  Purchase #5 $207.57   12.756%   $234.0476   $234.05   $234.05   $234.00  
  Purchase #6 $74.73   4.446%   $78.0525   $78.05   $78.05   $78.10  
  Purchase #7 $246.39   7.151%   $264.0093   $264.01   $264.00   $264.00  
  7 purchase totals = $1,095.29       $1,195.0448   $1,195.04   $1,195.00   $1,195.10