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 $196.26   4.318%   $204.7345   $204.73   $204.75   $204.70  
  Purchase #2 $169.96   3.641%   $176.1482   $176.15   $176.15   $176.10  
  Purchase #3 $181.97   8.830%   $198.038   $198.04   $198.05   $198.00  
  Purchase #4 $153.70   5.521%   $162.1858   $162.19   $162.20   $162.20  
  Purchase #5 $156.42   6.142%   $166.0273   $166.03   $166.05   $166.00  
  Purchase #6 $39.40   9.653%   $43.2033   $43.20   $43.20   $43.20  
  Purchase #7 $61.95   9.729%   $67.9771   $67.98   $68.00   $68.00  
  7 purchase totals = $959.66       $1,018.3142   $1,018.32   $1,018.40   $1,018.20