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 $44.58   5.214%   $46.9044   $46.90   $46.90   $46.90  
  Purchase #2 $210.79   12.533%   $237.2083   $237.21   $237.20   $237.20  
  Purchase #3 $151.93   6.459%   $161.7432   $161.74   $161.75   $161.70  
  Purchase #4 $161.54   8.442%   $175.1772   $175.18   $175.20   $175.20  
  Purchase #5 $246.81   7.619%   $265.6145   $265.61   $265.60   $265.60  
  Purchase #6 $244.87   13.192%   $277.1733   $277.17   $277.15   $277.20  
  Purchase #7 $31.86   11.770%   $35.6099   $35.61   $35.60   $35.60  
  7 purchase totals = $1,092.38       $1,199.4308   $1,199.42   $1,199.40   $1,199.40