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 $86.28   11.597%   $96.2859   $96.29   $96.30   $96.30  
  Purchase #2 $147.29   3.330%   $152.1948   $152.19   $152.20   $152.20  
  Purchase #3 $213.38   4.488%   $222.9565   $222.96   $222.95   $223.00  
  Purchase #4 $220.64   3.201%   $227.7027   $227.70   $227.70   $227.70  
  Purchase #5 $229.46   9.140%   $250.4326   $250.43   $250.45   $250.40  
  Purchase #6 $214.57   9.829%   $235.6601   $235.66   $235.65   $235.70  
  Purchase #7 $166.25   7.484%   $178.6922   $178.69   $178.70   $178.70  
  7 purchase totals = $1,277.87       $1,363.9248   $1,363.92   $1,363.95   $1,364.00