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 $43.77   11.258%   $48.6976   $48.70   $48.70   $48.70  
  Purchase #2 $215.44   4.552%   $225.2468   $225.25   $225.25   $225.20  
  Purchase #3 $162.80   7.803%   $175.5033   $175.50   $175.50   $175.50  
  Purchase #4 $247.47   11.436%   $275.7707   $275.77   $275.75   $275.80  
  Purchase #5 $102.36   6.343%   $108.8527   $108.85   $108.85   $108.90  
  Purchase #6 $125.89   12.116%   $141.1428   $141.14   $141.15   $141.10  
  Purchase #7 $116.26   6.634%   $123.9727   $123.97   $123.95   $124.00  
  7 purchase totals = $1,013.99       $1,099.1866   $1,099.18   $1,099.15   $1,099.20