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 $58.81   5.646%   $62.1304   $62.13   $62.15   $62.10  
  Purchase #2 $235.84   6.626%   $251.4668   $251.47   $251.45   $251.50  
  Purchase #3 $121.54   6.815%   $129.823   $129.82   $129.80   $129.80  
  Purchase #4 $52.79   3.660%   $54.7221   $54.72   $54.70   $54.70  
  Purchase #5 $230.38   10.763%   $255.1758   $255.18   $255.20   $255.20  
  Purchase #6 $209.40   4.512%   $218.8481   $218.85   $218.85   $218.80  
  Purchase #7 $228.90   7.373%   $245.7768   $245.78   $245.80   $245.80  
  7 purchase totals = $1,137.66       $1,217.9430   $1,217.95   $1,217.95   $1,217.90