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 $61.26   12.133%   $68.6927   $68.69   $68.70   $68.70  
  Purchase #2 $217.94   8.860%   $237.2495   $237.25   $237.25   $237.20  
  Purchase #3 $185.69   7.760%   $200.0995   $200.10   $200.10   $200.10  
  Purchase #4 $54.52   3.197%   $56.263   $56.26   $56.25   $56.30  
  Purchase #5 $57.77   4.332%   $60.2726   $60.27   $60.25   $60.30  
  Purchase #6 $104.76   6.550%   $111.6218   $111.62   $111.60   $111.60  
  Purchase #7 $231.53   12.634%   $260.7815   $260.78   $260.80   $260.80  
  7 purchase totals = $913.47       $994.9806   $994.97   $994.95   $995.00