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 $93.70   4.850%   $98.2445   $98.24   $98.25   $98.20  
  Purchase #2 $126.51   6.515%   $134.7521   $134.75   $134.75   $134.80  
  Purchase #3 $111.98   4.749%   $117.2979   $117.30   $117.30   $117.30  
  Purchase #4 $235.60   11.211%   $262.0131   $262.01   $262.00   $262.00  
  Purchase #5 $67.47   10.760%   $74.7298   $74.73   $74.75   $74.70  
  Purchase #6 $51.76   12.676%   $58.3211   $58.32   $58.30   $58.30  
  Purchase #7 $20.29   10.414%   $22.403   $22.40   $22.40   $22.40  
  7 purchase totals = $707.31       $767.7615   $767.75   $767.75   $767.70