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 $165.26   10.691%   $182.9279   $182.93   $182.95   $182.90  
  Purchase #2 $192.74   12.218%   $216.289   $216.29   $216.30   $216.30  
  Purchase #3 $199.32   12.872%   $224.9765   $224.98   $225.00   $225.00  
  Purchase #4 $225.53   6.640%   $240.5052   $240.51   $240.50   $240.50  
  Purchase #5 $119.81   13.384%   $135.8454   $135.85   $135.85   $135.80  
  Purchase #6 $230.60   11.566%   $257.2712   $257.27   $257.25   $257.30  
  Purchase #7 $100.68   3.826%   $104.532   $104.53   $104.55   $104.50  
  7 purchase totals = $1,233.94       $1,362.3472   $1,362.36   $1,362.40   $1,362.30