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 $114.41   4.249%   $119.2713   $119.27   $119.25   $119.30  
  Purchase #2 $61.51   8.338%   $66.6387   $66.64   $66.65   $66.60  
  Purchase #3 $237.78   3.768%   $246.7396   $246.74   $246.75   $246.70  
  Purchase #4 $132.48   4.429%   $138.3475   $138.35   $138.35   $138.30  
  Purchase #5 $167.54   3.781%   $173.8747   $173.87   $173.85   $173.90  
  Purchase #6 $116.90   6.568%   $124.578   $124.58   $124.60   $124.60  
  Purchase #7 $243.68   9.439%   $266.681   $266.68   $266.70   $266.70  
  7 purchase totals = $1,074.30       $1,136.1308   $1,136.13   $1,136.15   $1,136.10