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 $204.49   4.395%   $213.4773   $213.48   $213.50   $213.50  
  Purchase #2 $206.58   12.548%   $232.5017   $232.50   $232.50   $232.50  
  Purchase #3 $185.80   5.566%   $196.1416   $196.14   $196.15   $196.10  
  Purchase #4 $55.53   5.455%   $58.5592   $58.56   $58.55   $58.60  
  Purchase #5 $156.89   9.753%   $172.1915   $172.19   $172.20   $172.20  
  Purchase #6 $219.37   9.362%   $239.9074   $239.91   $239.90   $239.90  
  Purchase #7 $224.29   12.445%   $252.2029   $252.20   $252.20   $252.20  
  7 purchase totals = $1,252.95       $1,364.9816   $1,364.98   $1,365.00   $1,365.00