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 $201.93   8.747%   $219.5928   $219.59   $219.60   $219.60  
  Purchase #2 $47.71   5.191%   $50.1866   $50.19   $50.20   $50.20  
  Purchase #3 $158.77   6.138%   $168.5153   $168.52   $168.50   $168.50  
  Purchase #4 $162.61   10.710%   $180.0255   $180.03   $180.05   $180.00  
  Purchase #5 $98.95   8.742%   $107.6002   $107.60   $107.60   $107.60  
  Purchase #6 $211.60   5.154%   $222.5059   $222.51   $222.50   $222.50  
  Purchase #7 $131.67   11.495%   $146.8055   $146.81   $146.80   $146.80  
  7 purchase totals = $1,013.24       $1,095.2318   $1,095.25   $1,095.25   $1,095.20