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 $55.62   11.581%   $62.0614   $62.06   $62.05   $62.10  
  Purchase #2 $78.51   10.188%   $86.5086   $86.51   $86.50   $86.50  
  Purchase #3 $130.33   3.484%   $134.8707   $134.87   $134.85   $134.90  
  Purchase #4 $153.92   10.362%   $169.8692   $169.87   $169.85   $169.90  
  Purchase #5 $102.49   10.594%   $113.3478   $113.35   $113.35   $113.30  
  Purchase #6 $143.79   11.379%   $160.1519   $160.15   $160.15   $160.20  
  Purchase #7 $23.37   3.852%   $24.2702   $24.27   $24.25   $24.30  
  7 purchase totals = $688.03       $751.0798   $751.08   $751.00   $751.20