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 $244.78   7.160%   $262.3062   $262.31   $262.30   $262.30  
  Purchase #2 $215.31   6.526%   $229.3611   $229.36   $229.35   $229.40  
  Purchase #3 $61.57   10.102%   $67.7898   $67.79   $67.80   $67.80  
  Purchase #4 $164.38   4.531%   $171.8281   $171.83   $171.85   $171.80  
  Purchase #5 $184.68   11.536%   $205.9847   $205.98   $206.00   $206.00  
  Purchase #6 $250.66   9.143%   $273.5778   $273.58   $273.60   $273.60  
  Purchase #7 $202.42   11.102%   $224.8927   $224.89   $224.90   $224.90  
  7 purchase totals = $1,323.80       $1,435.7404   $1,435.74   $1,435.80   $1,435.80