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 $61.33   13.451%   $69.5795   $69.58   $69.60   $69.60  
  Purchase #2 $170.88   4.579%   $178.7046   $178.70   $178.70   $178.70  
  Purchase #3 $226.46   12.110%   $253.8843   $253.88   $253.90   $253.90  
  Purchase #4 $144.96   6.476%   $154.3476   $154.35   $154.35   $154.30  
  Purchase #5 $191.33   7.440%   $205.565   $205.57   $205.55   $205.60  
  Purchase #6 $49.52   3.310%   $51.1591   $51.16   $51.15   $51.20  
  Purchase #7 $202.52   12.228%   $227.2841   $227.28   $227.30   $227.30  
  7 purchase totals = $1,047.00       $1,140.5242   $1,140.52   $1,140.55   $1,140.60