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 $59.84   4.659%   $62.6279   $62.63   $62.65   $62.60  
  Purchase #2 $182.25   12.606%   $205.2244   $205.22   $205.20   $205.20  
  Purchase #3 $182.48   11.738%   $203.8995   $203.90   $203.90   $203.90  
  Purchase #4 $41.98   4.846%   $44.0144   $44.01   $44.00   $44.00  
  Purchase #5 $204.51   4.610%   $213.9379   $213.94   $213.95   $213.90  
  Purchase #6 $162.80   3.831%   $169.0369   $169.04   $169.05   $169.00  
  Purchase #7 $122.67   9.296%   $134.0734   $134.07   $134.05   $134.10  
  7 purchase totals = $956.53       $1,032.8144   $1,032.81   $1,032.80   $1,032.70