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 $195.84   8.566%   $212.6157   $212.62   $212.60   $212.60  
  Purchase #2 $100.56   3.540%   $104.1198   $104.12   $104.10   $104.10  
  Purchase #3 $74.29   13.663%   $84.4402   $84.44   $84.45   $84.40  
  Purchase #4 $11.41   3.172%   $11.7719   $11.77   $11.75   $11.80  
  Purchase #5 $115.98   7.352%   $124.5068   $124.51   $124.50   $124.50  
  Purchase #6 $181.94   11.686%   $203.2015   $203.20   $203.20   $203.20  
  Purchase #7 $196.68   4.744%   $206.0105   $206.01   $206.00   $206.00  
  7 purchase totals = $876.70       $946.6664   $946.67   $946.60   $946.60