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 $38.42   13.791%   $43.7185   $43.72   $43.70   $43.70  
  Purchase #2 $187.61   13.340%   $212.6372   $212.64   $212.65   $212.60  
  Purchase #3 $150.77   10.831%   $167.0999   $167.10   $167.10   $167.10  
  Purchase #4 $241.92   10.658%   $267.7038   $267.70   $267.70   $267.70  
  Purchase #5 $201.70   7.279%   $216.3817   $216.38   $216.40   $216.40  
  Purchase #6 $157.72   4.128%   $164.2307   $164.23   $164.25   $164.20  
  Purchase #7 $43.65   8.338%   $47.2895   $47.29   $47.30   $47.30  
  7 purchase totals = $1,021.79       $1,119.0613   $1,119.06   $1,119.10   $1,119.00