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 $57.66   8.324%   $62.4596   $62.46   $62.45   $62.50  
  Purchase #2 $197.33   11.464%   $219.9519   $219.95   $219.95   $220.00  
  Purchase #3 $68.96   8.321%   $74.6982   $74.70   $74.70   $74.70  
  Purchase #4 $228.48   7.788%   $246.274   $246.27   $246.25   $246.30  
  Purchase #5 $16.39   12.482%   $18.4358   $18.44   $18.45   $18.40  
  Purchase #6 $166.37   10.151%   $183.2582   $183.26   $183.25   $183.30  
  Purchase #7 $224.82   13.651%   $255.5102   $255.51   $255.50   $255.50  
  7 purchase totals = $960.01       $1,060.5879   $1,060.59   $1,060.55   $1,060.70