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 $236.65   7.457%   $254.297   $254.30   $254.30   $254.30  
  Purchase #2 $221.79   3.298%   $229.1046   $229.10   $229.10   $229.10  
  Purchase #3 $158.35   11.452%   $176.4842   $176.48   $176.50   $176.50  
  Purchase #4 $23.96   8.290%   $25.9463   $25.95   $25.95   $25.90  
  Purchase #5 $238.61   9.467%   $261.1992   $261.20   $261.20   $261.20  
  Purchase #6 $241.74   11.147%   $268.6868   $268.69   $268.70   $268.70  
  Purchase #7 $45.25   5.181%   $47.5944   $47.59   $47.60   $47.60  
  7 purchase totals = $1,166.35       $1,263.3125   $1,263.31   $1,263.35   $1,263.30