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 $206.71   3.502%   $213.949   $213.95   $213.95   $213.90  
  Purchase #2 $102.68   10.417%   $113.3762   $113.38   $113.40   $113.40  
  Purchase #3 $57.74   12.119%   $64.7375   $64.74   $64.75   $64.70  
  Purchase #4 $70.66   4.326%   $73.7168   $73.72   $73.70   $73.70  
  Purchase #5 $220.92   9.386%   $241.6556   $241.66   $241.65   $241.70  
  Purchase #6 $81.88   8.162%   $88.563   $88.56   $88.55   $88.60  
  Purchase #7 $201.82   6.509%   $214.9565   $214.96   $214.95   $215.00  
  7 purchase totals = $942.41       $1,010.9546   $1,010.97   $1,010.95   $1,011.00