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 $86.27   9.769%   $94.6977   $94.70   $94.70   $94.70  
  Purchase #2 $214.54   10.755%   $237.6138   $237.61   $237.60   $237.60  
  Purchase #3 $230.77   4.196%   $240.4531   $240.45   $240.45   $240.50  
  Purchase #4 $233.89   3.657%   $242.4434   $242.44   $242.45   $242.40  
  Purchase #5 $42.52   9.368%   $46.5033   $46.50   $46.50   $46.50  
  Purchase #6 $5.89   8.264%   $6.3767   $6.38   $6.40   $6.40  
  Purchase #7 $159.99   11.742%   $178.776   $178.78   $178.80   $178.80  
  7 purchase totals = $973.87       $1,046.8640   $1,046.86   $1,046.90   $1,046.90