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 $195.48   5.716%   $206.6536   $206.65   $206.65   $206.70  
  Purchase #2 $161.51   7.502%   $173.6265   $173.63   $173.65   $173.60  
  Purchase #3 $156.73   5.405%   $165.2013   $165.20   $165.20   $165.20  
  Purchase #4 $23.60   8.284%   $25.555   $25.56   $25.55   $25.60  
  Purchase #5 $181.78   11.747%   $203.1337   $203.13   $203.15   $203.10  
  Purchase #6 $94.59   10.250%   $104.2855   $104.29   $104.30   $104.30  
  Purchase #7 $63.64   7.703%   $68.5422   $68.54   $68.55   $68.50  
  7 purchase totals = $877.33       $946.9978   $947.00   $947.05   $947.00