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 $61.95   10.864%   $68.6802   $68.68   $68.70   $68.70  
  Purchase #2 $218.57   7.770%   $235.5529   $235.55   $235.55   $235.60  
  Purchase #3 $57.46   12.261%   $64.5052   $64.51   $64.50   $64.50  
  Purchase #4 $178.43   11.290%   $198.5747   $198.57   $198.55   $198.60  
  Purchase #5 $226.34   10.250%   $249.5399   $249.54   $249.55   $249.50  
  Purchase #6 $231.82   6.672%   $247.287   $247.29   $247.30   $247.30  
  Purchase #7 $35.92   6.679%   $38.3191   $38.32   $38.30   $38.30  
  7 purchase totals = $1,010.49       $1,102.4590   $1,102.46   $1,102.45   $1,102.50