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 $125.43   12.607%   $141.243   $141.24   $141.25   $141.20  
  Purchase #2 $228.56   3.784%   $237.2087   $237.21   $237.20   $237.20  
  Purchase #3 $56.79   5.604%   $59.9725   $59.97   $59.95   $60.00  
  Purchase #4 $191.55   7.584%   $206.0772   $206.08   $206.10   $206.10  
  Purchase #5 $248.30   11.795%   $277.587   $277.59   $277.60   $277.60  
  Purchase #6 $236.96   7.207%   $254.0377   $254.04   $254.05   $254.00  
  Purchase #7 $248.42   10.285%   $273.97   $273.97   $273.95   $274.00  
  7 purchase totals = $1,336.01       $1,450.0961   $1,450.10   $1,450.10   $1,450.10