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 $201.75   11.122%   $224.1886   $224.19   $224.20   $224.20  
  Purchase #2 $208.34   3.627%   $215.8965   $215.90   $215.90   $215.90  
  Purchase #3 $147.97   4.839%   $155.1303   $155.13   $155.15   $155.10  
  Purchase #4 $79.38   4.349%   $82.8322   $82.83   $82.85   $82.80  
  Purchase #5 $64.99   13.536%   $73.787   $73.79   $73.80   $73.80  
  Purchase #6 $54.62   10.184%   $60.1825   $60.18   $60.20   $60.20  
  Purchase #7 $75.81   8.231%   $82.0499   $82.05   $82.05   $82.00  
  7 purchase totals = $832.86       $894.0670   $894.07   $894.15   $894.00