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 $93.63   4.724%   $98.0531   $98.05   $98.05   $98.10  
  Purchase #2 $181.26   10.282%   $199.8972   $199.90   $199.90   $199.90  
  Purchase #3 $108.53   5.309%   $114.2919   $114.29   $114.30   $114.30  
  Purchase #4 $241.46   10.691%   $267.2745   $267.27   $267.25   $267.30  
  Purchase #5 $99.37   11.694%   $110.9903   $110.99   $111.00   $111.00  
  Purchase #6 $204.93   4.785%   $214.7359   $214.74   $214.75   $214.70  
  Purchase #7 $184.52   11.445%   $205.6383   $205.64   $205.65   $205.60  
  7 purchase totals = $1,113.70       $1,210.8812   $1,210.88   $1,210.90   $1,210.90