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 $208.48   11.339%   $232.1195   $232.12   $232.10   $232.10  
  Purchase #2 $86.31   10.678%   $95.5262   $95.53   $95.55   $95.50  
  Purchase #3 $209.86   7.842%   $226.3172   $226.32   $226.30   $226.30  
  Purchase #4 $214.94   10.616%   $237.758   $237.76   $237.75   $237.80  
  Purchase #5 $102.77   4.664%   $107.5632   $107.56   $107.55   $107.60  
  Purchase #6 $88.34   4.654%   $92.4513   $92.45   $92.45   $92.50  
  Purchase #7 $108.73   4.781%   $113.9284   $113.93   $113.95   $113.90  
  7 purchase totals = $1,019.43       $1,105.6638   $1,105.67   $1,105.65   $1,105.70