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 $58.86   4.796%   $61.6829   $61.68   $61.70   $61.70  
  Purchase #2 $126.34   12.510%   $142.1451   $142.15   $142.15   $142.10  
  Purchase #3 $187.42   3.534%   $194.0434   $194.04   $194.05   $194.00  
  Purchase #4 $101.68   6.262%   $108.0472   $108.05   $108.05   $108.00  
  Purchase #5 $209.97   11.772%   $234.6877   $234.69   $234.70   $234.70  
  Purchase #6 $163.58   4.376%   $170.7383   $170.74   $170.75   $170.70  
  Purchase #7 $49.80   13.457%   $56.5016   $56.50   $56.50   $56.50  
  7 purchase totals = $897.65       $967.8462   $967.85   $967.90   $967.70