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 $114.56   3.542%   $118.6177   $118.62   $118.60   $118.60  
  Purchase #2 $154.69   5.156%   $162.6658   $162.67   $162.65   $162.70  
  Purchase #3 $197.92   13.606%   $224.849   $224.85   $224.85   $224.80  
  Purchase #4 $23.61   13.687%   $26.8415   $26.84   $26.85   $26.80  
  Purchase #5 $213.40   10.404%   $235.6021   $235.60   $235.60   $235.60  
  Purchase #6 $230.76   13.726%   $262.4341   $262.43   $262.45   $262.40  
  Purchase #7 $59.52   8.401%   $64.5203   $64.52   $64.50   $64.50  
  7 purchase totals = $994.46       $1,095.5305   $1,095.53   $1,095.50   $1,095.40