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 $116.60   8.588%   $126.6136   $126.61   $126.60   $126.60  
  Purchase #2 $237.63   11.769%   $265.5967   $265.60   $265.60   $265.60  
  Purchase #3 $120.72   10.555%   $133.462   $133.46   $133.45   $133.50  
  Purchase #4 $101.38   10.280%   $111.8019   $111.80   $111.80   $111.80  
  Purchase #5 $171.50   9.175%   $187.2351   $187.24   $187.25   $187.20  
  Purchase #6 $19.80   11.180%   $22.0136   $22.01   $22.00   $22.00  
  Purchase #7 $250.80   6.519%   $267.1497   $267.15   $267.15   $267.10  
  7 purchase totals = $1,018.43       $1,113.8726   $1,113.87   $1,113.85   $1,113.80