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 $88.37   9.355%   $96.637   $96.64   $96.65   $96.60  
  Purchase #2 $94.99   8.591%   $103.1506   $103.15   $103.15   $103.20  
  Purchase #3 $207.77   13.522%   $235.8647   $235.86   $235.85   $235.90  
  Purchase #4 $217.65   7.602%   $234.1958   $234.20   $234.20   $234.20  
  Purchase #5 $223.91   7.812%   $241.4018   $241.40   $241.40   $241.40  
  Purchase #6 $21.59   4.519%   $22.5657   $22.57   $22.55   $22.60  
  Purchase #7 $25.99   6.822%   $27.763   $27.76   $27.75   $27.80  
  7 purchase totals = $880.27       $961.5786   $961.58   $961.55   $961.70