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 $184.97   11.856%   $206.9   $206.90   $206.90   $206.90  
  Purchase #2 $241.99   11.625%   $270.1213   $270.12   $270.10   $270.10  
  Purchase #3 $58.95   4.145%   $61.3935   $61.39   $61.40   $61.40  
  Purchase #4 $190.48   13.474%   $216.1453   $216.15   $216.15   $216.10  
  Purchase #5 $228.64   12.452%   $257.1103   $257.11   $257.10   $257.10  
  Purchase #6 $66.59   9.623%   $72.998   $73.00   $73.00   $73.00  
  Purchase #7 $162.47   11.498%   $181.1508   $181.15   $181.15   $181.20  
  7 purchase totals = $1,134.09       $1,265.8192   $1,265.82   $1,265.80   $1,265.80