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 $59.30   5.699%   $62.6795   $62.68   $62.70   $62.70  
  Purchase #2 $234.75   7.273%   $251.8234   $251.82   $251.80   $251.80  
  Purchase #3 $191.44   9.159%   $208.974   $208.97   $208.95   $209.00  
  Purchase #4 $150.76   12.833%   $170.107   $170.11   $170.10   $170.10  
  Purchase #5 $53.90   13.330%   $61.0849   $61.08   $61.10   $61.10  
  Purchase #6 $73.46   6.157%   $77.9829   $77.98   $78.00   $78.00  
  Purchase #7 $114.48   4.227%   $119.3191   $119.32   $119.30   $119.30  
  7 purchase totals = $878.09       $951.9708   $951.96   $951.95   $952.00