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 $160.80   9.183%   $175.5663   $175.57   $175.55   $175.60  
  Purchase #2 $118.35   3.696%   $122.7242   $122.72   $122.70   $122.70  
  Purchase #3 $16.60   11.824%   $18.5628   $18.56   $18.55   $18.60  
  Purchase #4 $244.73   9.223%   $267.3014   $267.30   $267.30   $267.30  
  Purchase #5 $36.54   6.133%   $38.781   $38.78   $38.80   $38.80  
  Purchase #6 $28.97   12.406%   $32.564   $32.56   $32.55   $32.60  
  Purchase #7 $119.81   6.239%   $127.2849   $127.28   $127.30   $127.30  
  7 purchase totals = $725.80       $782.7846   $782.77   $782.75   $782.90