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 $158.74   6.493%   $169.047   $169.05   $169.05   $169.00  
  Purchase #2 $123.80   7.795%   $133.4502   $133.45   $133.45   $133.50  
  Purchase #3 $80.28   8.332%   $86.9689   $86.97   $86.95   $87.00  
  Purchase #4 $186.68   13.370%   $211.6391   $211.64   $211.65   $211.60  
  Purchase #5 $200.95   8.319%   $217.667   $217.67   $217.65   $217.70  
  Purchase #6 $184.40   3.199%   $190.299   $190.30   $190.30   $190.30  
  Purchase #7 $20.25   13.226%   $22.9283   $22.93   $22.95   $22.90  
  7 purchase totals = $955.10       $1,031.9995   $1,032.01   $1,032.00   $1,032.00