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 $57.86   6.664%   $61.7158   $61.72   $61.70   $61.70  
  Purchase #2 $126.25   6.599%   $134.5812   $134.58   $134.60   $134.60  
  Purchase #3 $234.54   8.312%   $254.035   $254.04   $254.05   $254.00  
  Purchase #4 $136.83   5.676%   $144.5965   $144.60   $144.60   $144.60  
  Purchase #5 $184.44   4.345%   $192.4539   $192.45   $192.45   $192.50  
  Purchase #6 $130.70   12.756%   $147.3721   $147.37   $147.35   $147.40  
  Purchase #7 $24.64   3.195%   $25.4272   $25.43   $25.45   $25.40  
  7 purchase totals = $895.26       $960.1817   $960.19   $960.20   $960.20