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 $220.49   7.654%   $237.3663   $237.37   $237.35   $237.40  
  Purchase #2 $188.60   9.399%   $206.3265   $206.33   $206.35   $206.30  
  Purchase #3 $141.80   9.858%   $155.7786   $155.78   $155.80   $155.80  
  Purchase #4 $90.77   4.115%   $94.5052   $94.51   $94.50   $94.50  
  Purchase #5 $124.55   12.838%   $140.5397   $140.54   $140.55   $140.50  
  Purchase #6 $149.63   8.829%   $162.8408   $162.84   $162.85   $162.80  
  Purchase #7 $191.68   6.858%   $204.8254   $204.83   $204.85   $204.80  
  7 purchase totals = $1,107.52       $1,202.1825   $1,202.20   $1,202.25   $1,202.10