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 $237.75   10.290%   $262.2145   $262.21   $262.20   $262.20  
  Purchase #2 $235.98   11.343%   $262.7472   $262.75   $262.75   $262.70  
  Purchase #3 $238.71   4.107%   $248.5138   $248.51   $248.50   $248.50  
  Purchase #4 $25.25   10.618%   $27.931   $27.93   $27.95   $27.90  
  Purchase #5 $114.75   11.158%   $127.5538   $127.55   $127.55   $127.60  
  Purchase #6 $226.26   5.182%   $237.9848   $237.98   $238.00   $238.00  
  Purchase #7 $189.71   5.564%   $200.2655   $200.27   $200.25   $200.30  
  7 purchase totals = $1,268.41       $1,367.2106   $1,367.20   $1,367.20   $1,367.20