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 $56.59   4.196%   $58.9645   $58.96   $58.95   $59.00  
  Purchase #2 $207.66   4.843%   $217.717   $217.72   $217.70   $217.70  
  Purchase #3 $162.31   3.626%   $168.1954   $168.20   $168.20   $168.20  
  Purchase #4 $211.78   4.734%   $221.8057   $221.81   $221.80   $221.80  
  Purchase #5 $99.30   5.808%   $105.0673   $105.07   $105.05   $105.10  
  Purchase #6 $65.44   4.174%   $68.1715   $68.17   $68.15   $68.20  
  Purchase #7 $177.53   4.188%   $184.965   $184.97   $184.95   $185.00  
  7 purchase totals = $980.61       $1,024.8864   $1,024.90   $1,024.80   $1,025.00