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 $190.82   6.184%   $202.6203   $202.62   $202.60   $202.60  
  Purchase #2 $184.91   6.215%   $196.4022   $196.40   $196.40   $196.40  
  Purchase #3 $116.26   4.399%   $121.3743   $121.37   $121.35   $121.40  
  Purchase #4 $6.59   13.443%   $7.4759   $7.48   $7.50   $7.50  
  Purchase #5 $145.97   5.751%   $154.3647   $154.36   $154.35   $154.40  
  Purchase #6 $166.88   3.576%   $172.8476   $172.85   $172.85   $172.80  
  Purchase #7 $242.91   3.698%   $251.8928   $251.89   $251.90   $251.90  
  7 purchase totals = $1,054.34       $1,106.9778   $1,106.97   $1,106.95   $1,107.00