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 $56.56   3.657%   $58.6284   $58.63   $58.65   $58.60  
  Purchase #2 $145.26   9.354%   $158.8476   $158.85   $158.85   $158.80  
  Purchase #3 $86.54   9.421%   $94.6929   $94.69   $94.70   $94.70  
  Purchase #4 $221.37   11.386%   $246.5752   $246.58   $246.60   $246.60  
  Purchase #5 $224.78   4.763%   $235.4863   $235.49   $235.50   $235.50  
  Purchase #6 $188.44   8.218%   $203.926   $203.93   $203.95   $203.90  
  Purchase #7 $98.88   7.763%   $106.5561   $106.56   $106.55   $106.60  
  7 purchase totals = $1,021.83       $1,104.7125   $1,104.73   $1,104.80   $1,104.70