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 $243.72   8.711%   $264.9504   $264.95   $264.95   $265.00  
  Purchase #2 $237.39   7.212%   $254.5106   $254.51   $254.50   $254.50  
  Purchase #3 $95.41   6.288%   $101.4094   $101.41   $101.40   $101.40  
  Purchase #4 $106.33   11.432%   $118.4856   $118.49   $118.50   $118.50  
  Purchase #5 $236.30   5.763%   $249.918   $249.92   $249.90   $249.90  
  Purchase #6 $226.91   11.409%   $252.7982   $252.80   $252.80   $252.80  
  Purchase #7 $230.30   8.715%   $250.3706   $250.37   $250.35   $250.40  
  7 purchase totals = $1,376.36       $1,492.4428   $1,492.45   $1,492.40   $1,492.50