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 $146.35   4.510%   $152.9504   $152.95   $152.95   $153.00  
  Purchase #2 $40.35   3.138%   $41.6162   $41.62   $41.60   $41.60  
  Purchase #3 $247.29   7.579%   $266.0321   $266.03   $266.05   $266.00  
  Purchase #4 $157.40   5.829%   $166.5748   $166.57   $166.55   $166.60  
  Purchase #5 $200.65   4.814%   $210.3093   $210.31   $210.30   $210.30  
  Purchase #6 $14.99   13.741%   $17.0498   $17.05   $17.05   $17.00  
  Purchase #7 $225.91   7.306%   $242.415   $242.42   $242.40   $242.40  
  7 purchase totals = $1,032.94       $1,096.9476   $1,096.95   $1,096.90   $1,096.90