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 $64.86   11.542%   $72.3461   $72.35   $72.35   $72.30  
  Purchase #2 $16.54   4.297%   $17.2507   $17.25   $17.25   $17.30  
  Purchase #3 $214.38   9.576%   $234.909   $234.91   $234.90   $234.90  
  Purchase #4 $120.78   4.799%   $126.5762   $126.58   $126.60   $126.60  
  Purchase #5 $140.37   6.297%   $149.2091   $149.21   $149.20   $149.20  
  Purchase #6 $188.83   5.586%   $199.378   $199.38   $199.40   $199.40  
  Purchase #7 $239.33   5.407%   $252.2706   $252.27   $252.25   $252.30  
  7 purchase totals = $985.09       $1,051.9397   $1,051.95   $1,051.95   $1,052.00