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 $41.28   6.242%   $43.8567   $43.86   $43.85   $43.90  
  Purchase #2 $233.93   10.345%   $258.1301   $258.13   $258.15   $258.10  
  Purchase #3 $202.35   3.703%   $209.843   $209.84   $209.85   $209.80  
  Purchase #4 $68.25   12.532%   $76.8031   $76.80   $76.80   $76.80  
  Purchase #5 $239.74   11.257%   $266.7275   $266.73   $266.75   $266.70  
  Purchase #6 $122.32   5.601%   $129.1711   $129.17   $129.15   $129.20  
  Purchase #7 $229.73   5.257%   $241.8069   $241.81   $241.80   $241.80  
  7 purchase totals = $1,137.60       $1,226.3384   $1,226.34   $1,226.35   $1,226.30