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 $105.47   8.297%   $114.2208   $114.22   $114.20   $114.20  
  Purchase #2 $177.25   10.310%   $195.5245   $195.52   $195.50   $195.50  
  Purchase #3 $137.48   3.687%   $142.5489   $142.55   $142.55   $142.50  
  Purchase #4 $130.52   13.656%   $148.3438   $148.34   $148.35   $148.30  
  Purchase #5 $161.56   8.671%   $175.5689   $175.57   $175.55   $175.60  
  Purchase #6 $134.44   8.102%   $145.3323   $145.33   $145.35   $145.30  
  Purchase #7 $242.93   7.412%   $260.936   $260.94   $260.95   $260.90  
  7 purchase totals = $1,089.65       $1,182.4752   $1,182.47   $1,182.45   $1,182.30