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 $183.37   7.540%   $197.1961   $197.20   $197.20   $197.20  
  Purchase #2 $93.33   12.826%   $105.3005   $105.30   $105.30   $105.30  
  Purchase #3 $99.65   4.103%   $103.7386   $103.74   $103.75   $103.70  
  Purchase #4 $76.52   6.529%   $81.516   $81.52   $81.50   $81.50  
  Purchase #5 $199.54   4.370%   $208.2599   $208.26   $208.25   $208.30  
  Purchase #6 $64.74   5.621%   $68.379   $68.38   $68.40   $68.40  
  Purchase #7 $21.38   8.853%   $23.2728   $23.27   $23.25   $23.30  
  7 purchase totals = $738.53       $787.6629   $787.67   $787.65   $787.70