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 $211.41   7.674%   $227.6336   $227.63   $227.65   $227.60  
  Purchase #2 $119.81   11.362%   $133.4228   $133.42   $133.40   $133.40  
  Purchase #3 $93.66   11.814%   $104.725   $104.73   $104.75   $104.70  
  Purchase #4 $165.38   12.379%   $185.8524   $185.85   $185.85   $185.90  
  Purchase #5 $233.44   9.822%   $256.3685   $256.37   $256.35   $256.40  
  Purchase #6 $246.95   6.764%   $263.6537   $263.65   $263.65   $263.70  
  Purchase #7 $31.67   7.391%   $34.0107   $34.01   $34.00   $34.00  
  7 purchase totals = $1,102.32       $1,205.6667   $1,205.66   $1,205.65   $1,205.70