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 $195.49   9.260%   $213.5924   $213.59   $213.60   $213.60  
  Purchase #2 $207.39   12.284%   $232.8658   $232.87   $232.85   $232.90  
  Purchase #3 $146.28   4.419%   $152.7441   $152.74   $152.75   $152.70  
  Purchase #4 $210.91   3.242%   $217.7477   $217.75   $217.75   $217.70  
  Purchase #5 $191.67   11.449%   $213.6143   $213.61   $213.60   $213.60  
  Purchase #6 $126.53   13.547%   $143.671   $143.67   $143.65   $143.70  
  Purchase #7 $176.45   10.115%   $194.2979   $194.30   $194.30   $194.30  
  7 purchase totals = $1,254.72       $1,368.5332   $1,368.53   $1,368.50   $1,368.50