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 $101.39   8.767%   $110.2789   $110.28   $110.30   $110.30  
  Purchase #2 $147.49   3.745%   $153.0135   $153.01   $153.00   $153.00  
  Purchase #3 $204.62   11.763%   $228.6895   $228.69   $228.70   $228.70  
  Purchase #4 $66.63   13.711%   $75.7656   $75.77   $75.75   $75.80  
  Purchase #5 $41.60   13.361%   $47.1582   $47.16   $47.15   $47.20  
  Purchase #6 $177.88   8.873%   $193.6633   $193.66   $193.65   $193.70  
  Purchase #7 $234.93   7.555%   $252.679   $252.68   $252.70   $252.70  
  7 purchase totals = $974.54       $1,061.2480   $1,061.25   $1,061.25   $1,061.40