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 $85.32   10.717%   $94.4637   $94.46   $94.45   $94.50  
  Purchase #2 $49.44   4.685%   $51.7563   $51.76   $51.75   $51.80  
  Purchase #3 $8.87   8.505%   $9.6244   $9.62   $9.60   $9.60  
  Purchase #4 $73.49   3.161%   $75.813   $75.81   $75.80   $75.80  
  Purchase #5 $11.47   7.654%   $12.3479   $12.35   $12.35   $12.30  
  Purchase #6 $52.59   4.700%   $55.0617   $55.06   $55.05   $55.10  
  Purchase #7 $59.85   4.344%   $62.4499   $62.45   $62.45   $62.40  
  7 purchase totals = $341.03       $361.5169   $361.51   $361.45   $361.50