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 $44.98   8.107%   $48.6265   $48.63   $48.65   $48.60  
  Purchase #2 $222.42   12.637%   $250.5272   $250.53   $250.55   $250.50  
  Purchase #3 $95.98   6.298%   $102.0248   $102.02   $102.00   $102.00  
  Purchase #4 $125.45   7.162%   $134.4347   $134.43   $134.45   $134.40  
  Purchase #5 $210.47   3.822%   $218.5142   $218.51   $218.50   $218.50  
  Purchase #6 $223.72   9.410%   $244.7721   $244.77   $244.75   $244.80  
  Purchase #7 $155.89   4.481%   $162.8754   $162.88   $162.90   $162.90  
  7 purchase totals = $1,078.91       $1,161.7749   $1,161.77   $1,161.80   $1,161.70