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 $104.72   8.558%   $113.6819   $113.68   $113.70   $113.70  
  Purchase #2 $195.59   7.428%   $210.1184   $210.12   $210.10   $210.10  
  Purchase #3 $23.87   6.406%   $25.3991   $25.40   $25.40   $25.40  
  Purchase #4 $54.52   6.159%   $57.8779   $57.88   $57.90   $57.90  
  Purchase #5 $33.27   5.864%   $35.221   $35.22   $35.20   $35.20  
  Purchase #6 $215.32   6.750%   $229.8541   $229.85   $229.85   $229.90  
  Purchase #7 $44.49   5.359%   $46.8742   $46.87   $46.85   $46.90  
  7 purchase totals = $671.78       $719.0266   $719.02   $719.00   $719.10