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 $236.70   4.337%   $246.9657   $246.97   $246.95   $247.00  
  Purchase #2 $172.90   3.124%   $178.3014   $178.30   $178.30   $178.30  
  Purchase #3 $217.37   4.665%   $227.5103   $227.51   $227.50   $227.50  
  Purchase #4 $95.99   4.773%   $100.5716   $100.57   $100.55   $100.60  
  Purchase #5 $194.82   7.168%   $208.7847   $208.78   $208.80   $208.80  
  Purchase #6 $143.81   6.173%   $152.6874   $152.69   $152.70   $152.70  
  Purchase #7 $77.35   4.103%   $80.5237   $80.52   $80.50   $80.50  
  7 purchase totals = $1,138.94       $1,195.3448   $1,195.34   $1,195.30   $1,195.40