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 $60.33   3.491%   $62.4361   $62.44   $62.45   $62.40  
  Purchase #2 $102.33   5.184%   $107.6348   $107.63   $107.65   $107.60  
  Purchase #3 $192.86   12.109%   $216.2134   $216.21   $216.20   $216.20  
  Purchase #4 $30.84   7.746%   $33.2289   $33.23   $33.25   $33.20  
  Purchase #5 $41.74   11.283%   $46.4495   $46.45   $46.45   $46.40  
  Purchase #6 $40.32   6.352%   $42.8811   $42.88   $42.90   $42.90  
  Purchase #7 $101.42   7.111%   $108.632   $108.63   $108.65   $108.60  
  7 purchase totals = $569.84       $617.4758   $617.47   $617.55   $617.30