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 $98.76   7.342%   $106.011   $106.01   $106.00   $106.00  
  Purchase #2 $109.97   4.824%   $115.275   $115.28   $115.30   $115.30  
  Purchase #3 $186.32   5.761%   $197.0539   $197.05   $197.05   $197.10  
  Purchase #4 $109.39   5.343%   $115.2347   $115.23   $115.25   $115.20  
  Purchase #5 $41.80   5.744%   $44.201   $44.20   $44.20   $44.20  
  Purchase #6 $182.38   13.691%   $207.3496   $207.35   $207.35   $207.30  
  Purchase #7 $151.48   6.860%   $161.8715   $161.87   $161.85   $161.90  
  7 purchase totals = $880.10       $946.9967   $946.99   $947.00   $947.00