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 $51.59   4.780%   $54.056   $54.06   $54.05   $54.10  
  Purchase #2 $113.69   8.803%   $123.6981   $123.70   $123.70   $123.70  
  Purchase #3 $186.31   6.460%   $198.3456   $198.35   $198.35   $198.30  
  Purchase #4 $218.76   10.153%   $240.9707   $240.97   $240.95   $241.00  
  Purchase #5 $214.72   6.637%   $228.971   $228.97   $228.95   $229.00  
  Purchase #6 $205.42   4.214%   $214.0764   $214.08   $214.10   $214.10  
  Purchase #7 $66.37   12.269%   $74.5129   $74.51   $74.50   $74.50  
  7 purchase totals = $1,056.86       $1,134.6307   $1,134.64   $1,134.60   $1,134.70