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 $208.84   5.685%   $220.7126   $220.71   $220.70   $220.70  
  Purchase #2 $118.30   5.322%   $124.5959   $124.60   $124.60   $124.60  
  Purchase #3 $130.93   6.372%   $139.2729   $139.27   $139.25   $139.30  
  Purchase #4 $41.92   11.844%   $46.885   $46.89   $46.90   $46.90  
  Purchase #5 $147.83   7.829%   $159.4036   $159.40   $159.40   $159.40  
  Purchase #6 $107.80   7.824%   $116.2343   $116.23   $116.25   $116.20  
  Purchase #7 $110.45   8.298%   $119.6151   $119.62   $119.60   $119.60  
  7 purchase totals = $866.07       $926.7194   $926.72   $926.70   $926.70