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 $98.93   3.297%   $102.1917   $102.19   $102.20   $102.20  
  Purchase #2 $206.67   12.598%   $232.7063   $232.71   $232.70   $232.70  
  Purchase #3 $60.71   11.550%   $67.722   $67.72   $67.70   $67.70  
  Purchase #4 $158.89   5.675%   $167.907   $167.91   $167.90   $167.90  
  Purchase #5 $144.27   5.135%   $151.6783   $151.68   $151.70   $151.70  
  Purchase #6 $198.33   12.829%   $223.7738   $223.77   $223.75   $223.80  
  Purchase #7 $204.90   6.579%   $218.3804   $218.38   $218.40   $218.40  
  7 purchase totals = $1,072.70       $1,164.3595   $1,164.36   $1,164.35   $1,164.40