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 $237.33   10.525%   $262.309   $262.31   $262.30   $262.30  
  Purchase #2 $41.92   4.872%   $43.9623   $43.96   $43.95   $44.00  
  Purchase #3 $51.89   11.460%   $57.8366   $57.84   $57.85   $57.80  
  Purchase #4 $134.92   12.854%   $152.2626   $152.26   $152.25   $152.30  
  Purchase #5 $244.27   7.341%   $262.2019   $262.20   $262.20   $262.20  
  Purchase #6 $190.78   9.166%   $208.2669   $208.27   $208.25   $208.30  
  Purchase #7 $232.31   10.820%   $257.4459   $257.45   $257.45   $257.40  
  7 purchase totals = $1,133.42       $1,244.2852   $1,244.29   $1,244.25   $1,244.30