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 $183.69   7.677%   $197.7919   $197.79   $197.80   $197.80  
  Purchase #2 $210.36   4.429%   $219.6768   $219.68   $219.70   $219.70  
  Purchase #3 $68.42   7.224%   $73.3627   $73.36   $73.35   $73.40  
  Purchase #4 $189.71   5.202%   $199.5787   $199.58   $199.60   $199.60  
  Purchase #5 $233.71   13.446%   $265.1346   $265.13   $265.15   $265.10  
  Purchase #6 $141.40   5.859%   $149.6846   $149.68   $149.70   $149.70  
  Purchase #7 $113.91   6.630%   $121.4622   $121.46   $121.45   $121.50  
  7 purchase totals = $1,141.20       $1,226.6915   $1,226.68   $1,226.75   $1,226.80