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 $62.43   11.384%   $69.537   $69.54   $69.55   $69.50  
  Purchase #2 $232.61   9.175%   $253.952   $253.95   $253.95   $254.00  
  Purchase #3 $215.56   3.332%   $222.7425   $222.74   $222.75   $222.70  
  Purchase #4 $11.53   10.618%   $12.7543   $12.75   $12.75   $12.80  
  Purchase #5 $203.41   11.771%   $227.3534   $227.35   $227.35   $227.40  
  Purchase #6 $106.60   10.691%   $117.9966   $118.00   $118.00   $118.00  
  Purchase #7 $93.76   11.109%   $104.1758   $104.18   $104.20   $104.20  
  7 purchase totals = $925.90       $1,008.5116   $1,008.51   $1,008.55   $1,008.60