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 $69.69   9.160%   $76.0736   $76.07   $76.05   $76.10  
  Purchase #2 $235.92   5.221%   $248.2374   $248.24   $248.25   $248.20  
  Purchase #3 $78.73   5.334%   $82.9295   $82.93   $82.95   $82.90  
  Purchase #4 $77.84   4.712%   $81.5078   $81.51   $81.50   $81.50  
  Purchase #5 $10.65   5.742%   $11.2615   $11.26   $11.25   $11.30  
  Purchase #6 $185.52   5.408%   $195.5529   $195.55   $195.55   $195.60  
  Purchase #7 $56.79   7.470%   $61.0322   $61.03   $61.05   $61.00  
  7 purchase totals = $715.14       $756.5949   $756.59   $756.60   $756.60