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 $54.53   11.418%   $60.7562   $60.76   $60.75   $60.80  
  Purchase #2 $199.73   9.425%   $218.5546   $218.55   $218.55   $218.60  
  Purchase #3 $157.56   13.503%   $178.8353   $178.84   $178.85   $178.80  
  Purchase #4 $61.50   11.456%   $68.5454   $68.55   $68.55   $68.50  
  Purchase #5 $245.43   3.804%   $254.7662   $254.77   $254.75   $254.80  
  Purchase #6 $196.96   4.662%   $206.1423   $206.14   $206.15   $206.10  
  Purchase #7 $126.35   12.836%   $142.5683   $142.57   $142.55   $142.60  
  7 purchase totals = $1,042.06       $1,130.1683   $1,130.18   $1,130.15   $1,130.20