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 $119.27   3.509%   $123.4552   $123.46   $123.45   $123.50  
  Purchase #2 $248.67   10.174%   $273.9697   $273.97   $273.95   $274.00  
  Purchase #3 $218.49   6.360%   $232.386   $232.39   $232.40   $232.40  
  Purchase #4 $93.50   9.538%   $102.418   $102.42   $102.40   $102.40  
  Purchase #5 $228.43   5.550%   $241.1079   $241.11   $241.10   $241.10  
  Purchase #6 $112.67   10.381%   $124.3663   $124.37   $124.35   $124.40  
  Purchase #7 $118.62   7.615%   $127.6529   $127.65   $127.65   $127.70  
  7 purchase totals = $1,139.65       $1,225.3560   $1,225.37   $1,225.30   $1,225.50