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 $214.64   12.422%   $241.3026   $241.30   $241.30   $241.30  
  Purchase #2 $157.68   4.606%   $164.9427   $164.94   $164.95   $164.90  
  Purchase #3 $162.83   6.235%   $172.9825   $172.98   $173.00   $173.00  
  Purchase #4 $70.75   7.687%   $76.1886   $76.19   $76.20   $76.20  
  Purchase #5 $227.80   5.631%   $240.6274   $240.63   $240.65   $240.60  
  Purchase #6 $23.98   11.456%   $26.7271   $26.73   $26.75   $26.70  
  Purchase #7 $156.66   8.319%   $169.6925   $169.69   $169.70   $169.70  
  7 purchase totals = $1,014.34       $1,092.4634   $1,092.46   $1,092.55   $1,092.40