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 $145.81   4.724%   $152.6981   $152.70   $152.70   $152.70  
  Purchase #2 $35.50   11.545%   $39.5985   $39.60   $39.60   $39.60  
  Purchase #3 $41.93   13.220%   $47.4731   $47.47   $47.45   $47.50  
  Purchase #4 $150.89   3.253%   $155.7985   $155.80   $155.80   $155.80  
  Purchase #5 $146.34   12.692%   $164.9135   $164.91   $164.90   $164.90  
  Purchase #6 $173.97   13.409%   $197.2976   $197.30   $197.30   $197.30  
  Purchase #7 $238.99   11.644%   $266.818   $266.82   $266.80   $266.80  
  7 purchase totals = $933.43       $1,024.5973   $1,024.60   $1,024.55   $1,024.60