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 $71.93   5.584%   $75.9466   $75.95   $75.95   $75.90  
  Purchase #2 $49.58   13.253%   $56.1508   $56.15   $56.15   $56.20  
  Purchase #3 $45.58   5.670%   $48.1644   $48.16   $48.15   $48.20  
  Purchase #4 $16.56   13.711%   $18.8305   $18.83   $18.85   $18.80  
  Purchase #5 $109.53   11.195%   $121.7919   $121.79   $121.80   $121.80  
  Purchase #6 $211.25   8.644%   $229.5105   $229.51   $229.50   $229.50  
  Purchase #7 $165.85   9.834%   $182.1597   $182.16   $182.15   $182.20  
  7 purchase totals = $670.28       $732.5544   $732.55   $732.55   $732.60