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 $41.30   10.775%   $45.7501   $45.75   $45.75   $45.80  
  Purchase #2 $73.93   10.495%   $81.689   $81.69   $81.70   $81.70  
  Purchase #3 $68.61   9.294%   $74.9866   $74.99   $75.00   $75.00  
  Purchase #4 $145.41   11.381%   $161.9591   $161.96   $161.95   $162.00  
  Purchase #5 $195.73   4.858%   $205.2386   $205.24   $205.25   $205.20  
  Purchase #6 $185.86   4.278%   $193.8111   $193.81   $193.80   $193.80  
  Purchase #7 $161.87   6.825%   $172.9176   $172.92   $172.90   $172.90  
  7 purchase totals = $872.71       $936.3521   $936.36   $936.35   $936.40