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 $44.96   7.579%   $48.3675   $48.37   $48.35   $48.40  
  Purchase #2 $201.27   9.827%   $221.0488   $221.05   $221.05   $221.00  
  Purchase #3 $127.89   6.722%   $136.4868   $136.49   $136.50   $136.50  
  Purchase #4 $73.73   5.179%   $77.5485   $77.55   $77.55   $77.50  
  Purchase #5 $80.85   10.815%   $89.5939   $89.59   $89.60   $89.60  
  Purchase #6 $229.80   12.759%   $259.1202   $259.12   $259.10   $259.10  
  Purchase #7 $148.47   9.845%   $163.0869   $163.09   $163.10   $163.10  
  7 purchase totals = $906.97       $995.2526   $995.26   $995.25   $995.20