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 $41.74   11.118%   $46.3807   $46.38   $46.40   $46.40  
  Purchase #2 $197.81   10.166%   $217.9194   $217.92   $217.90   $217.90  
  Purchase #3 $77.65   9.381%   $84.9343   $84.93   $84.95   $84.90  
  Purchase #4 $29.44   12.131%   $33.0114   $33.01   $33.00   $33.00  
  Purchase #5 $60.51   9.495%   $66.2554   $66.26   $66.25   $66.30  
  Purchase #6 $49.37   5.649%   $52.1589   $52.16   $52.15   $52.20  
  Purchase #7 $193.86   3.503%   $200.6509   $200.65   $200.65   $200.70  
  7 purchase totals = $650.38       $701.3110   $701.31   $701.30   $701.40