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 $118.26   6.393%   $125.8204   $125.82   $125.80   $125.80  
  Purchase #2 $36.92   13.430%   $41.8784   $41.88   $41.90   $41.90  
  Purchase #3 $150.35   12.463%   $169.0881   $169.09   $169.10   $169.10  
  Purchase #4 $148.69   5.260%   $156.5111   $156.51   $156.50   $156.50  
  Purchase #5 $219.37   6.417%   $233.447   $233.45   $233.45   $233.40  
  Purchase #6 $242.54   11.408%   $270.209   $270.21   $270.20   $270.20  
  Purchase #7 $176.45   12.391%   $198.3139   $198.31   $198.30   $198.30  
  7 purchase totals = $1,092.58       $1,195.2679   $1,195.27   $1,195.25   $1,195.20