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 $86.52   10.626%   $95.7136   $95.71   $95.70   $95.70  
  Purchase #2 $31.89   12.579%   $35.9014   $35.90   $35.90   $35.90  
  Purchase #3 $186.87   13.772%   $212.6057   $212.61   $212.60   $212.60  
  Purchase #4 $204.34   12.185%   $229.2388   $229.24   $229.25   $229.20  
  Purchase #5 $41.61   10.479%   $45.9703   $45.97   $45.95   $46.00  
  Purchase #6 $206.36   12.742%   $232.6544   $232.65   $232.65   $232.70  
  Purchase #7 $37.63   9.176%   $41.0829   $41.08   $41.10   $41.10  
  7 purchase totals = $795.22       $893.1671   $893.16   $893.15   $893.20