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 $41.90   12.775%   $47.2527   $47.25   $47.25   $47.30  
  Purchase #2 $217.42   13.356%   $246.4586   $246.46   $246.45   $246.50  
  Purchase #3 $200.82   11.853%   $224.6232   $224.62   $224.60   $224.60  
  Purchase #4 $171.65   3.205%   $177.1514   $177.15   $177.15   $177.20  
  Purchase #5 $197.97   11.339%   $220.4178   $220.42   $220.40   $220.40  
  Purchase #6 $16.98   4.334%   $17.7159   $17.72   $17.70   $17.70  
  Purchase #7 $153.63   5.240%   $161.6802   $161.68   $161.70   $161.70  
  7 purchase totals = $1,000.37       $1,095.2998   $1,095.30   $1,095.25   $1,095.40