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 $200.46   8.279%   $217.0561   $217.06   $217.05   $217.10  
  Purchase #2 $180.41   9.518%   $197.5814   $197.58   $197.60   $197.60  
  Purchase #3 $67.86   8.269%   $73.4713   $73.47   $73.45   $73.50  
  Purchase #4 $88.86   6.679%   $94.795   $94.80   $94.80   $94.80  
  Purchase #5 $194.91   5.458%   $205.5482   $205.55   $205.55   $205.50  
  Purchase #6 $59.46   4.635%   $62.216   $62.22   $62.20   $62.20  
  Purchase #7 $236.72   6.335%   $251.7162   $251.72   $251.70   $251.70  
  7 purchase totals = $1,028.68       $1,102.3842   $1,102.40   $1,102.35   $1,102.40