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 $44.75   5.811%   $47.3504   $47.35   $47.35   $47.40  
  Purchase #2 $196.63   11.437%   $219.1186   $219.12   $219.10   $219.10  
  Purchase #3 $215.79   6.376%   $229.5488   $229.55   $229.55   $229.50  
  Purchase #4 $168.70   8.665%   $183.3179   $183.32   $183.30   $183.30  
  Purchase #5 $133.80   8.755%   $145.5142   $145.51   $145.50   $145.50  
  Purchase #6 $102.37   6.500%   $109.0241   $109.02   $109.00   $109.00  
  Purchase #7 $8.99   13.748%   $10.2259   $10.23   $10.25   $10.20  
  7 purchase totals = $871.03       $944.0999   $944.10   $944.05   $944.00