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 $61.62   9.570%   $67.517   $67.52   $67.50   $67.50  
  Purchase #2 $175.54   13.424%   $199.1045   $199.10   $199.10   $199.10  
  Purchase #3 $38.27   10.483%   $42.2818   $42.28   $42.30   $42.30  
  Purchase #4 $232.83   5.687%   $246.071   $246.07   $246.05   $246.10  
  Purchase #5 $84.47   12.711%   $95.207   $95.21   $95.20   $95.20  
  Purchase #6 $62.29   3.597%   $64.5306   $64.53   $64.55   $64.50  
  Purchase #7 $200.28   5.656%   $211.6078   $211.61   $211.60   $211.60  
  7 purchase totals = $855.30       $926.3197   $926.32   $926.30   $926.30