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 $55.77   11.120%   $61.9716   $61.97   $61.95   $62.00  
  Purchase #2 $229.60   5.204%   $241.5484   $241.55   $241.55   $241.50  
  Purchase #3 $213.25   7.371%   $228.9687   $228.97   $228.95   $229.00  
  Purchase #4 $19.46   5.211%   $20.4741   $20.47   $20.45   $20.50  
  Purchase #5 $121.82   9.708%   $133.6463   $133.65   $133.65   $133.60  
  Purchase #6 $21.64   10.400%   $23.8906   $23.89   $23.90   $23.90  
  Purchase #7 $157.65   4.611%   $164.9192   $164.92   $164.90   $164.90  
  7 purchase totals = $819.19       $875.4189   $875.42   $875.35   $875.40