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 $58.74   3.753%   $60.9445   $60.94   $60.95   $60.90  
  Purchase #2 $214.79   8.714%   $233.5068   $233.51   $233.50   $233.50  
  Purchase #3 $93.48   3.656%   $96.8976   $96.90   $96.90   $96.90  
  Purchase #4 $43.78   8.546%   $47.5214   $47.52   $47.50   $47.50  
  Purchase #5 $207.31   6.358%   $220.4908   $220.49   $220.50   $220.50  
  Purchase #6 $42.42   11.682%   $47.3755   $47.38   $47.40   $47.40  
  Purchase #7 $228.99   5.730%   $242.1111   $242.11   $242.10   $242.10  
  7 purchase totals = $889.51       $948.8477   $948.85   $948.85   $948.80