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 $69.75   9.479%   $76.3616   $76.36   $76.35   $76.40  
  Purchase #2 $204.25   7.805%   $220.1917   $220.19   $220.20   $220.20  
  Purchase #3 $73.49   11.381%   $81.8539   $81.85   $81.85   $81.90  
  Purchase #4 $73.99   5.283%   $77.8989   $77.90   $77.90   $77.90  
  Purchase #5 $219.92   5.277%   $231.5252   $231.53   $231.55   $231.50  
  Purchase #6 $145.97   3.794%   $151.5081   $151.51   $151.50   $151.50  
  Purchase #7 $175.57   4.681%   $183.7884   $183.79   $183.80   $183.80  
  7 purchase totals = $962.94       $1,023.1278   $1,023.13   $1,023.15   $1,023.20