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 $176.96   11.688%   $197.6431   $197.64   $197.65   $197.60  
  Purchase #2 $195.95   10.816%   $217.144   $217.14   $217.15   $217.10  
  Purchase #3 $98.55   5.294%   $103.7672   $103.77   $103.75   $103.80  
  Purchase #4 $248.57   8.732%   $270.2751   $270.28   $270.30   $270.30  
  Purchase #5 $166.81   3.282%   $172.2847   $172.28   $172.30   $172.30  
  Purchase #6 $156.26   12.752%   $176.1863   $176.19   $176.20   $176.20  
  Purchase #7 $148.79   9.569%   $163.0277   $163.03   $163.05   $163.00  
  7 purchase totals = $1,191.89       $1,300.3281   $1,300.33   $1,300.40   $1,300.30