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 $178.44   9.826%   $195.9735   $195.97   $195.95   $196.00  
  Purchase #2 $203.69   7.681%   $219.3354   $219.34   $219.35   $219.30  
  Purchase #3 $249.48   10.742%   $276.2791   $276.28   $276.30   $276.30  
  Purchase #4 $15.25   6.129%   $16.1847   $16.18   $16.20   $16.20  
  Purchase #5 $163.96   6.519%   $174.6486   $174.65   $174.65   $174.60  
  Purchase #6 $205.67   4.450%   $214.8223   $214.82   $214.80   $214.80  
  Purchase #7 $162.66   9.742%   $178.5063   $178.51   $178.50   $178.50  
  7 purchase totals = $1,179.15       $1,275.7499   $1,275.75   $1,275.75   $1,275.70