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 $90.38   5.683%   $95.5163   $95.52   $95.50   $95.50  
  Purchase #2 $226.28   8.818%   $246.2334   $246.23   $246.25   $246.20  
  Purchase #3 $117.60   7.628%   $126.5705   $126.57   $126.55   $126.60  
  Purchase #4 $221.87   4.287%   $231.3816   $231.38   $231.40   $231.40  
  Purchase #5 $62.87   3.267%   $64.924   $64.92   $64.90   $64.90  
  Purchase #6 $79.77   4.296%   $83.1969   $83.20   $83.20   $83.20  
  Purchase #7 $179.27   9.865%   $196.955   $196.96   $196.95   $197.00  
  7 purchase totals = $978.04       $1,044.7777   $1,044.78   $1,044.75   $1,044.80