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 $182.52   6.493%   $194.371   $194.37   $194.35   $194.40  
  Purchase #2 $170.28   3.628%   $176.4578   $176.46   $176.45   $176.50  
  Purchase #3 $103.83   11.264%   $115.5254   $115.53   $115.55   $115.50  
  Purchase #4 $68.91   10.214%   $75.9485   $75.95   $75.95   $75.90  
  Purchase #5 $115.47   7.775%   $124.4478   $124.45   $124.45   $124.40  
  Purchase #6 $137.89   7.822%   $148.6758   $148.68   $148.70   $148.70  
  Purchase #7 $178.64   6.841%   $190.8608   $190.86   $190.85   $190.90  
  7 purchase totals = $957.54       $1,026.2871   $1,026.30   $1,026.30   $1,026.30