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 $191.29   13.402%   $216.9267   $216.93   $216.95   $216.90  
  Purchase #2 $165.97   7.849%   $178.997   $179.00   $179.00   $179.00  
  Purchase #3 $177.79   11.716%   $198.6199   $198.62   $198.60   $198.60  
  Purchase #4 $59.95   9.440%   $65.6093   $65.61   $65.60   $65.60  
  Purchase #5 $157.94   8.456%   $171.2954   $171.30   $171.30   $171.30  
  Purchase #6 $175.83   10.254%   $193.8596   $193.86   $193.85   $193.90  
  Purchase #7 $204.77   7.243%   $219.6015   $219.60   $219.60   $219.60  
  7 purchase totals = $1,133.54       $1,244.9094   $1,244.92   $1,244.90   $1,244.90