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 $58.44   6.262%   $62.0995   $62.10   $62.10   $62.10  
  Purchase #2 $217.71   5.384%   $229.4315   $229.43   $229.45   $229.40  
  Purchase #3 $249.54   8.535%   $270.8382   $270.84   $270.85   $270.80  
  Purchase #4 $142.39   12.124%   $159.6534   $159.65   $159.65   $159.70  
  Purchase #5 $34.62   3.550%   $35.849   $35.85   $35.85   $35.80  
  Purchase #6 $194.73   4.617%   $203.7207   $203.72   $203.70   $203.70  
  Purchase #7 $129.92   4.660%   $135.9743   $135.97   $135.95   $136.00  
  7 purchase totals = $1,027.35       $1,097.5666   $1,097.56   $1,097.55   $1,097.50