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 $85.36   11.343%   $95.0424   $95.04   $95.05   $95.00  
  Purchase #2 $107.43   7.842%   $115.8547   $115.85   $115.85   $115.90  
  Purchase #3 $242.87   9.839%   $266.766   $266.77   $266.75   $266.80  
  Purchase #4 $208.28   13.284%   $235.9479   $235.95   $235.95   $235.90  
  Purchase #5 $116.62   4.170%   $121.4831   $121.48   $121.50   $121.50  
  Purchase #6 $188.31   12.707%   $212.2386   $212.24   $212.25   $212.20  
  Purchase #7 $38.78   12.277%   $43.541   $43.54   $43.55   $43.50  
  7 purchase totals = $987.65       $1,090.8737   $1,090.87   $1,090.90   $1,090.80