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 $90.52   5.648%   $95.6326   $95.63   $95.65   $95.60  
  Purchase #2 $159.95   11.326%   $178.0659   $178.07   $178.05   $178.10  
  Purchase #3 $176.98   11.524%   $197.3752   $197.38   $197.40   $197.40  
  Purchase #4 $44.54   13.252%   $50.4424   $50.44   $50.45   $50.40  
  Purchase #5 $23.52   6.370%   $25.0182   $25.02   $25.00   $25.00  
  Purchase #6 $183.76   12.646%   $206.9983   $207.00   $207.00   $207.00  
  Purchase #7 $173.51   8.413%   $188.1074   $188.11   $188.10   $188.10  
  7 purchase totals = $852.78       $941.6400   $941.65   $941.65   $941.60