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 $47.72   9.607%   $52.3045   $52.30   $52.30   $52.30  
  Purchase #2 $89.51   4.658%   $93.6794   $93.68   $93.70   $93.70  
  Purchase #3 $97.75   10.348%   $107.8652   $107.87   $107.85   $107.90  
  Purchase #4 $188.36   3.713%   $195.3538   $195.35   $195.35   $195.40  
  Purchase #5 $85.71   13.873%   $97.6005   $97.60   $97.60   $97.60  
  Purchase #6 $235.99   4.508%   $246.6284   $246.63   $246.65   $246.60  
  Purchase #7 $92.62   7.634%   $99.6906   $99.69   $99.70   $99.70  
  7 purchase totals = $837.66       $893.1224   $893.12   $893.15   $893.20