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 $86.53   10.539%   $95.6494   $95.65   $95.65   $95.60  
  Purchase #2 $157.52   11.261%   $175.2583   $175.26   $175.25   $175.30  
  Purchase #3 $60.77   11.844%   $67.9676   $67.97   $67.95   $68.00  
  Purchase #4 $28.78   6.619%   $30.6849   $30.68   $30.70   $30.70  
  Purchase #5 $180.98   3.321%   $186.9903   $186.99   $187.00   $187.00  
  Purchase #6 $171.78   7.645%   $184.9126   $184.91   $184.90   $184.90  
  Purchase #7 $144.69   11.158%   $160.8345   $160.83   $160.85   $160.80  
  7 purchase totals = $831.05       $902.2976   $902.29   $902.30   $902.30