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 $201.73   6.240%   $214.318   $214.32   $214.30   $214.30  
  Purchase #2 $196.52   8.263%   $212.7584   $212.76   $212.75   $212.80  
  Purchase #3 $46.85   8.705%   $50.9283   $50.93   $50.95   $50.90  
  Purchase #4 $222.25   5.685%   $234.8849   $234.88   $234.90   $234.90  
  Purchase #5 $210.54   8.425%   $228.278   $228.28   $228.30   $228.30  
  Purchase #6 $192.88   3.457%   $199.5479   $199.55   $199.55   $199.50  
  Purchase #7 $215.33   5.572%   $227.3282   $227.33   $227.35   $227.30  
  7 purchase totals = $1,286.10       $1,368.0437   $1,368.05   $1,368.10   $1,368.00