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 $88.68   5.368%   $93.4403   $93.44   $93.45   $93.40  
  Purchase #2 $155.39   9.108%   $169.5429   $169.54   $169.55   $169.50  
  Purchase #3 $239.84   11.362%   $267.0906   $267.09   $267.10   $267.10  
  Purchase #4 $192.59   8.239%   $208.4575   $208.46   $208.45   $208.50  
  Purchase #5 $119.56   8.541%   $129.7716   $129.77   $129.75   $129.80  
  Purchase #6 $61.78   10.285%   $68.1341   $68.13   $68.15   $68.10  
  Purchase #7 $152.82   7.820%   $164.7705   $164.77   $164.75   $164.80  
  7 purchase totals = $1,010.66       $1,101.2075   $1,101.20   $1,101.20   $1,101.20