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 $155.96   7.306%   $167.3544   $167.35   $167.35   $167.40  
  Purchase #2 $62.35   13.800%   $70.9543   $70.95   $70.95   $71.00  
  Purchase #3 $110.64   7.509%   $118.948   $118.95   $118.95   $118.90  
  Purchase #4 $219.28   7.818%   $236.4233   $236.42   $236.40   $236.40  
  Purchase #5 $250.29   9.389%   $273.7897   $273.79   $273.80   $273.80  
  Purchase #6 $46.25   12.517%   $52.0391   $52.04   $52.05   $52.00  
  Purchase #7 $237.85   4.172%   $247.7731   $247.77   $247.75   $247.80  
  7 purchase totals = $1,082.62       $1,167.2819   $1,167.27   $1,167.25   $1,167.30