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 $169.27   7.469%   $181.9128   $181.91   $181.90   $181.90  
  Purchase #2 $198.85   4.428%   $207.6551   $207.66   $207.65   $207.70  
  Purchase #3 $127.71   3.728%   $132.471   $132.47   $132.45   $132.50  
  Purchase #4 $147.56   10.325%   $162.7956   $162.80   $162.80   $162.80  
  Purchase #5 $206.70   5.227%   $217.5042   $217.50   $217.50   $217.50  
  Purchase #6 $163.96   4.728%   $171.712   $171.71   $171.70   $171.70  
  Purchase #7 $180.90   6.751%   $193.1126   $193.11   $193.10   $193.10  
  7 purchase totals = $1,194.95       $1,267.1633   $1,267.16   $1,267.10   $1,267.20