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 $92.78   3.625%   $96.1433   $96.14   $96.15   $96.10  
  Purchase #2 $198.99   10.761%   $220.4033   $220.40   $220.40   $220.40  
  Purchase #3 $84.32   13.716%   $95.8853   $95.89   $95.90   $95.90  
  Purchase #4 $162.99   5.244%   $171.5372   $171.54   $171.55   $171.50  
  Purchase #5 $98.66   5.121%   $103.7124   $103.71   $103.70   $103.70  
  Purchase #6 $203.45   5.432%   $214.5014   $214.50   $214.50   $214.50  
  Purchase #7 $192.75   8.480%   $209.0952   $209.10   $209.10   $209.10  
  7 purchase totals = $1,033.94       $1,111.2781   $1,111.28   $1,111.30   $1,111.20