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 $159.36   10.822%   $176.6059   $176.61   $176.60   $176.60  
  Purchase #2 $245.66   7.249%   $263.4679   $263.47   $263.45   $263.50  
  Purchase #3 $156.95   4.438%   $163.9154   $163.92   $163.90   $163.90  
  Purchase #4 $41.35   4.843%   $43.3526   $43.35   $43.35   $43.40  
  Purchase #5 $151.78   7.118%   $162.5837   $162.58   $162.60   $162.60  
  Purchase #6 $200.85   5.290%   $211.475   $211.48   $211.50   $211.50  
  Purchase #7 $156.28   10.508%   $172.7019   $172.70   $172.70   $172.70  
  7 purchase totals = $1,112.23       $1,194.1024   $1,194.11   $1,194.10   $1,194.20