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 $153.80   5.742%   $162.6312   $162.63   $162.65   $162.60  
  Purchase #2 $208.37   11.205%   $231.7179   $231.72   $231.70   $231.70  
  Purchase #3 $243.79   11.394%   $271.5674   $271.57   $271.55   $271.60  
  Purchase #4 $91.91   10.692%   $101.737   $101.74   $101.75   $101.70  
  Purchase #5 $249.37   5.774%   $263.7686   $263.77   $263.75   $263.80  
  Purchase #6 $69.71   9.768%   $76.5193   $76.52   $76.50   $76.50  
  Purchase #7 $231.31   11.819%   $258.6485   $258.65   $258.65   $258.60  
  7 purchase totals = $1,248.26       $1,366.5899   $1,366.60   $1,366.55   $1,366.50