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 $126.50   4.792%   $132.5619   $132.56   $132.55   $132.60  
  Purchase #2 $119.99   4.425%   $125.2996   $125.30   $125.30   $125.30  
  Purchase #3 $77.99   12.528%   $87.7606   $87.76   $87.75   $87.80  
  Purchase #4 $195.45   7.141%   $209.4071   $209.41   $209.40   $209.40  
  Purchase #5 $95.50   4.764%   $100.0496   $100.05   $100.05   $100.00  
  Purchase #6 $240.81   3.109%   $248.2968   $248.30   $248.30   $248.30  
  Purchase #7 $138.52   12.710%   $156.1259   $156.13   $156.15   $156.10  
  7 purchase totals = $994.76       $1,059.5015   $1,059.51   $1,059.50   $1,059.50