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 $196.79   6.779%   $210.1304   $210.13   $210.15   $210.10  
  Purchase #2 $174.54   11.322%   $194.3014   $194.30   $194.30   $194.30  
  Purchase #3 $192.39   11.616%   $214.738   $214.74   $214.75   $214.70  
  Purchase #4 $41.70   8.108%   $45.081   $45.08   $45.10   $45.10  
  Purchase #5 $157.97   11.105%   $175.5126   $175.51   $175.50   $175.50  
  Purchase #6 $8.44   13.190%   $9.5532   $9.55   $9.55   $9.60  
  Purchase #7 $240.82   5.807%   $254.8044   $254.80   $254.80   $254.80  
  7 purchase totals = $1,012.65       $1,104.1210   $1,104.11   $1,104.15   $1,104.10