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 $206.76   7.536%   $222.3414   $222.34   $222.35   $222.30  
  Purchase #2 $223.89   9.220%   $244.5327   $244.53   $244.55   $244.50  
  Purchase #3 $84.80   12.447%   $95.3551   $95.36   $95.35   $95.40  
  Purchase #4 $136.79   11.549%   $152.5879   $152.59   $152.60   $152.60  
  Purchase #5 $165.77   7.537%   $178.2641   $178.26   $178.25   $178.30  
  Purchase #6 $14.89   11.741%   $16.6382   $16.64   $16.65   $16.60  
  Purchase #7 $192.88   11.652%   $215.3544   $215.35   $215.35   $215.40  
  7 purchase totals = $1,025.78       $1,125.0738   $1,125.07   $1,125.10   $1,125.10