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 $215.45   4.708%   $225.5934   $225.59   $225.60   $225.60  
  Purchase #2 $246.31   4.283%   $256.8595   $256.86   $256.85   $256.90  
  Purchase #3 $239.97   9.377%   $262.472   $262.47   $262.45   $262.50  
  Purchase #4 $236.85   4.263%   $246.9469   $246.95   $246.95   $246.90  
  Purchase #5 $237.42   6.129%   $251.9715   $251.97   $251.95   $252.00  
  Purchase #6 $11.74   13.289%   $13.3001   $13.30   $13.30   $13.30  
  Purchase #7 $159.99   11.585%   $178.5248   $178.52   $178.50   $178.50  
  7 purchase totals = $1,347.73       $1,435.6682   $1,435.66   $1,435.60   $1,435.70