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 $208.43   12.741%   $234.9861   $234.99   $235.00   $235.00  
  Purchase #2 $82.86   13.251%   $93.8398   $93.84   $93.85   $93.80  
  Purchase #3 $176.50   11.202%   $196.2715   $196.27   $196.25   $196.30  
  Purchase #4 $238.45   11.262%   $265.3042   $265.30   $265.30   $265.30  
  Purchase #5 $151.98   7.224%   $162.959   $162.96   $162.95   $163.00  
  Purchase #6 $49.78   12.422%   $55.9637   $55.96   $55.95   $56.00  
  Purchase #7 $110.83   12.514%   $124.6993   $124.70   $124.70   $124.70  
  7 purchase totals = $1,018.83       $1,134.0236   $1,134.02   $1,134.00   $1,134.10