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 $157.82   11.267%   $175.6016   $175.60   $175.60   $175.60  
  Purchase #2 $34.67   8.348%   $37.5643   $37.56   $37.55   $37.60  
  Purchase #3 $236.53   3.445%   $244.6785   $244.68   $244.70   $244.70  
  Purchase #4 $46.69   12.638%   $52.5907   $52.59   $52.60   $52.60  
  Purchase #5 $247.64   4.354%   $258.4222   $258.42   $258.40   $258.40  
  Purchase #6 $52.49   10.471%   $57.9862   $57.99   $58.00   $58.00  
  Purchase #7 $219.95   9.542%   $240.9376   $240.94   $240.95   $240.90  
  7 purchase totals = $995.79       $1,067.7811   $1,067.78   $1,067.80   $1,067.80