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 $182.88   6.722%   $195.1732   $195.17   $195.15   $195.20  
  Purchase #2 $246.84   6.348%   $262.5094   $262.51   $262.50   $262.50  
  Purchase #3 $241.49   7.185%   $258.8411   $258.84   $258.85   $258.80  
  Purchase #4 $45.97   9.675%   $50.4176   $50.42   $50.40   $50.40  
  Purchase #5 $68.60   6.108%   $72.7901   $72.79   $72.80   $72.80  
  Purchase #6 $175.31   5.197%   $184.4209   $184.42   $184.40   $184.40  
  Purchase #7 $24.65   9.163%   $26.9087   $26.91   $26.90   $26.90  
  7 purchase totals = $985.74       $1,051.0610   $1,051.06   $1,051.00   $1,051.00