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 $141.27   7.781%   $152.2622   $152.26   $152.25   $152.30  
  Purchase #2 $43.91   11.727%   $49.0593   $49.06   $49.05   $49.10  
  Purchase #3 $148.76   9.430%   $162.7881   $162.79   $162.80   $162.80  
  Purchase #4 $216.36   6.140%   $229.6445   $229.64   $229.65   $229.60  
  Purchase #5 $181.81   12.424%   $204.3981   $204.40   $204.40   $204.40  
  Purchase #6 $96.63   3.681%   $100.187   $100.19   $100.20   $100.20  
  Purchase #7 $146.68   10.685%   $162.3528   $162.35   $162.35   $162.40  
  7 purchase totals = $975.42       $1,060.6920   $1,060.69   $1,060.70   $1,060.80