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 $118.31   5.664%   $125.0111   $125.01   $125.00   $125.00  
  Purchase #2 $134.82   9.828%   $148.0701   $148.07   $148.05   $148.10  
  Purchase #3 $191.66   10.182%   $211.1748   $211.17   $211.15   $211.20  
  Purchase #4 $102.27   5.124%   $107.5103   $107.51   $107.50   $107.50  
  Purchase #5 $170.96   8.524%   $185.5326   $185.53   $185.55   $185.50  
  Purchase #6 $232.42   8.733%   $252.7172   $252.72   $252.70   $252.70  
  Purchase #7 $58.97   10.241%   $65.0091   $65.01   $65.00   $65.00  
  7 purchase totals = $1,009.41       $1,095.0252   $1,095.02   $1,094.95   $1,095.00