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 $91.53   5.488%   $96.5532   $96.55   $96.55   $96.60  
  Purchase #2 $177.45   3.564%   $183.7743   $183.77   $183.75   $183.80  
  Purchase #3 $42.62   8.822%   $46.3799   $46.38   $46.40   $46.40  
  Purchase #4 $119.29   10.215%   $131.4755   $131.48   $131.50   $131.50  
  Purchase #5 $85.92   8.241%   $93.0007   $93.00   $93.00   $93.00  
  Purchase #6 $31.39   7.573%   $33.7672   $33.77   $33.75   $33.80  
  Purchase #7 $111.53   5.754%   $117.9474   $117.95   $117.95   $117.90  
  7 purchase totals = $659.73       $702.8982   $702.90   $702.90   $703.00