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 $215.25   5.323%   $226.7078   $226.71   $226.70   $226.70  
  Purchase #2 $217.34   9.472%   $237.9264   $237.93   $237.95   $237.90  
  Purchase #3 $116.78   12.179%   $131.0026   $131.00   $131.00   $131.00  
  Purchase #4 $24.93   13.618%   $28.325   $28.33   $28.35   $28.30  
  Purchase #5 $216.49   3.742%   $224.5911   $224.59   $224.60   $224.60  
  Purchase #6 $216.69   4.141%   $225.6631   $225.66   $225.65   $225.70  
  Purchase #7 $224.80   6.807%   $240.1021   $240.10   $240.10   $240.10  
  7 purchase totals = $1,232.28       $1,314.3181   $1,314.32   $1,314.35   $1,314.30