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 $88.86   7.223%   $95.2784   $95.28   $95.30   $95.30  
  Purchase #2 $185.54   11.297%   $206.5005   $206.50   $206.50   $206.50  
  Purchase #3 $56.53   8.299%   $61.2214   $61.22   $61.20   $61.20  
  Purchase #4 $223.60   5.388%   $235.6476   $235.65   $235.65   $235.60  
  Purchase #5 $94.43   6.284%   $100.364   $100.36   $100.35   $100.40  
  Purchase #6 $196.63   9.307%   $214.9304   $214.93   $214.95   $214.90  
  Purchase #7 $156.86   13.288%   $177.7036   $177.70   $177.70   $177.70  
  7 purchase totals = $1,002.45       $1,091.6459   $1,091.64   $1,091.65   $1,091.60