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 $243.38   7.757%   $262.259   $262.26   $262.25   $262.30  
  Purchase #2 $98.85   8.852%   $107.6002   $107.60   $107.60   $107.60  
  Purchase #3 $19.47   11.114%   $21.6339   $21.63   $21.65   $21.60  
  Purchase #4 $218.55   3.624%   $226.4703   $226.47   $226.45   $226.50  
  Purchase #5 $57.67   3.267%   $59.5541   $59.55   $59.55   $59.60  
  Purchase #6 $79.52   7.732%   $85.6685   $85.67   $85.65   $85.70  
  Purchase #7 $139.84   5.846%   $148.015   $148.02   $148.00   $148.00  
  7 purchase totals = $857.28       $911.2010   $911.20   $911.15   $911.30