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 $224.75   7.361%   $241.2938   $241.29   $241.30   $241.30  
  Purchase #2 $32.99   13.157%   $37.3305   $37.33   $37.35   $37.30  
  Purchase #3 $166.84   11.198%   $185.5227   $185.52   $185.50   $185.50  
  Purchase #4 $208.37   9.356%   $227.8651   $227.87   $227.85   $227.90  
  Purchase #5 $250.52   9.435%   $274.1566   $274.16   $274.15   $274.20  
  Purchase #6 $177.63   11.434%   $197.9402   $197.94   $197.95   $197.90  
  Purchase #7 $8.52   9.439%   $9.3242   $9.32   $9.30   $9.30  
  7 purchase totals = $1,069.62       $1,173.4331   $1,173.43   $1,173.40   $1,173.40