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 $65.38   4.869%   $68.5634   $68.56   $68.55   $68.60  
  Purchase #2 $84.32   9.138%   $92.0252   $92.03   $92.05   $92.00  
  Purchase #3 $232.57   6.179%   $246.9405   $246.94   $246.95   $246.90  
  Purchase #4 $101.53   13.371%   $115.1056   $115.11   $115.10   $115.10  
  Purchase #5 $59.79   6.641%   $63.7607   $63.76   $63.75   $63.80  
  Purchase #6 $201.62   5.865%   $213.445   $213.45   $213.45   $213.40  
  Purchase #7 $184.98   5.635%   $195.4036   $195.40   $195.40   $195.40  
  7 purchase totals = $930.19       $995.2440   $995.25   $995.25   $995.20