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 $68.86   11.731%   $76.938   $76.94   $76.95   $76.90  
  Purchase #2 $190.46   11.629%   $212.6086   $212.61   $212.60   $212.60  
  Purchase #3 $45.33   4.141%   $47.2071   $47.21   $47.20   $47.20  
  Purchase #4 $127.48   4.382%   $133.0662   $133.07   $133.05   $133.10  
  Purchase #5 $242.27   5.826%   $256.3847   $256.38   $256.40   $256.40  
  Purchase #6 $124.59   5.319%   $131.2169   $131.22   $131.20   $131.20  
  Purchase #7 $247.93   11.869%   $277.3568   $277.36   $277.35   $277.40  
  7 purchase totals = $1,046.92       $1,134.7783   $1,134.79   $1,134.75   $1,134.80