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 $69.51   9.314%   $75.9842   $75.98   $76.00   $76.00  
  Purchase #2 $250.35   4.640%   $261.9662   $261.97   $261.95   $262.00  
  Purchase #3 $156.66   13.654%   $178.0504   $178.05   $178.05   $178.10  
  Purchase #4 $167.78   12.468%   $188.6988   $188.70   $188.70   $188.70  
  Purchase #5 $58.48   4.261%   $60.9718   $60.97   $60.95   $61.00  
  Purchase #6 $217.83   11.573%   $243.0395   $243.04   $243.05   $243.00  
  Purchase #7 $171.39   3.775%   $177.86   $177.86   $177.85   $177.90  
  7 purchase totals = $1,092.00       $1,186.5709   $1,186.57   $1,186.55   $1,186.70