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 $119.58   5.694%   $126.3889   $126.39   $126.40   $126.40  
  Purchase #2 $71.83   4.351%   $74.9553   $74.96   $74.95   $75.00  
  Purchase #3 $78.97   7.279%   $84.7182   $84.72   $84.70   $84.70  
  Purchase #4 $47.95   6.635%   $51.1315   $51.13   $51.15   $51.10  
  Purchase #5 $224.36   5.166%   $235.9504   $235.95   $235.95   $236.00  
  Purchase #6 $80.53   8.676%   $87.5168   $87.52   $87.50   $87.50  
  Purchase #7 $52.84   8.635%   $57.4027   $57.40   $57.40   $57.40  
  7 purchase totals = $676.06       $718.0638   $718.07   $718.05   $718.10