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 $167.92   11.735%   $187.6254   $187.63   $187.65   $187.60  
  Purchase #2 $26.83   13.615%   $30.4829   $30.48   $30.50   $30.50  
  Purchase #3 $210.69   13.779%   $239.721   $239.72   $239.70   $239.70  
  Purchase #4 $121.78   6.373%   $129.541   $129.54   $129.55   $129.50  
  Purchase #5 $93.90   9.135%   $102.4778   $102.48   $102.50   $102.50  
  Purchase #6 $200.50   9.395%   $219.337   $219.34   $219.35   $219.30  
  Purchase #7 $173.41   7.102%   $185.7256   $185.73   $185.75   $185.70  
  7 purchase totals = $995.03       $1,094.9107   $1,094.92   $1,095.00   $1,094.80