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 $102.82   10.830%   $113.9554   $113.96   $113.95   $114.00  
  Purchase #2 $41.78   3.769%   $43.3547   $43.35   $43.35   $43.40  
  Purchase #3 $143.97   11.822%   $160.9901   $160.99   $161.00   $161.00  
  Purchase #4 $181.77   6.588%   $193.745   $193.75   $193.75   $193.70  
  Purchase #5 $242.44   9.132%   $264.5796   $264.58   $264.60   $264.60  
  Purchase #6 $206.74   3.782%   $214.5589   $214.56   $214.55   $214.60  
  Purchase #7 $184.44   13.542%   $209.4169   $209.42   $209.40   $209.40  
  7 purchase totals = $1,103.96       $1,200.6006   $1,200.61   $1,200.60   $1,200.70