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 $208.58   9.498%   $228.3909   $228.39   $228.40   $228.40  
  Purchase #2 $223.86   12.283%   $251.3567   $251.36   $251.35   $251.40  
  Purchase #3 $96.34   6.384%   $102.4903   $102.49   $102.50   $102.50  
  Purchase #4 $217.50   10.240%   $239.772   $239.77   $239.75   $239.80  
  Purchase #5 $130.45   7.439%   $140.1542   $140.15   $140.15   $140.20  
  Purchase #6 $15.68   4.343%   $16.361   $16.36   $16.35   $16.40  
  Purchase #7 $180.78   4.411%   $188.7542   $188.75   $188.75   $188.80  
  7 purchase totals = $1,073.19       $1,167.2793   $1,167.27   $1,167.25   $1,167.50