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 $151.39   8.697%   $164.5564   $164.56   $164.55   $164.60  
  Purchase #2 $248.84   3.670%   $257.9724   $257.97   $257.95   $258.00  
  Purchase #3 $89.44   3.372%   $92.4559   $92.46   $92.45   $92.50  
  Purchase #4 $165.38   3.200%   $170.6722   $170.67   $170.65   $170.70  
  Purchase #5 $123.85   6.286%   $131.6352   $131.64   $131.65   $131.60  
  Purchase #6 $144.30   3.450%   $149.2784   $149.28   $149.30   $149.30  
  Purchase #7 $212.26   10.700%   $234.9718   $234.97   $234.95   $235.00  
  7 purchase totals = $1,135.46       $1,201.5423   $1,201.55   $1,201.50   $1,201.70