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 $13.32   7.601%   $14.3325   $14.33   $14.35   $14.30  
  Purchase #2 $184.65   9.776%   $202.7014   $202.70   $202.70   $202.70  
  Purchase #3 $162.66   9.368%   $177.898   $177.90   $177.90   $177.90  
  Purchase #4 $172.99   12.510%   $194.631   $194.63   $194.65   $194.60  
  Purchase #5 $218.71   11.199%   $243.2033   $243.20   $243.20   $243.20  
  Purchase #6 $162.84   4.782%   $170.627   $170.63   $170.65   $170.60  
  Purchase #7 $57.81   6.752%   $61.7133   $61.71   $61.70   $61.70  
  7 purchase totals = $972.98       $1,065.1065   $1,065.10   $1,065.15   $1,065.00