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 $157.37   11.814%   $175.9617   $175.96   $175.95   $176.00  
  Purchase #2 $31.35   12.602%   $35.3007   $35.30   $35.30   $35.30  
  Purchase #3 $214.91   11.759%   $240.1813   $240.18   $240.20   $240.20  
  Purchase #4 $52.43   10.306%   $57.8334   $57.83   $57.85   $57.80  
  Purchase #5 $183.80   12.134%   $206.1023   $206.10   $206.10   $206.10  
  Purchase #6 $91.90   4.298%   $95.8499   $95.85   $95.85   $95.80  
  Purchase #7 $223.49   11.413%   $248.9969   $249.00   $249.00   $249.00  
  7 purchase totals = $955.25       $1,060.2262   $1,060.22   $1,060.25   $1,060.20