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 $103.98   10.398%   $114.7918   $114.79   $114.80   $114.80  
  Purchase #2 $29.55   13.871%   $33.6489   $33.65   $33.65   $33.60  
  Purchase #3 $7.99   8.304%   $8.6535   $8.65   $8.65   $8.70  
  Purchase #4 $50.87   6.311%   $54.0804   $54.08   $54.10   $54.10  
  Purchase #5 $214.46   6.564%   $228.5372   $228.54   $228.55   $228.50  
  Purchase #6 $240.85   5.785%   $254.7832   $254.78   $254.80   $254.80  
  Purchase #7 $11.78   8.343%   $12.7628   $12.76   $12.75   $12.80  
  7 purchase totals = $659.48       $707.2578   $707.25   $707.30   $707.30