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 $190.96   7.364%   $205.0223   $205.02   $205.00   $205.00  
  Purchase #2 $166.30   7.505%   $178.7808   $178.78   $178.80   $178.80  
  Purchase #3 $250.97   8.376%   $271.9912   $271.99   $272.00   $272.00  
  Purchase #4 $195.83   7.808%   $211.1204   $211.12   $211.10   $211.10  
  Purchase #5 $231.53   7.412%   $248.691   $248.69   $248.70   $248.70  
  Purchase #6 $152.87   5.699%   $161.5821   $161.58   $161.60   $161.60  
  Purchase #7 $80.26   13.815%   $91.3479   $91.35   $91.35   $91.30  
  7 purchase totals = $1,268.72       $1,368.5357   $1,368.53   $1,368.55   $1,368.50