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 $80.95   7.361%   $86.9087   $86.91   $86.90   $86.90  
  Purchase #2 $235.30   13.599%   $267.2984   $267.30   $267.30   $267.30  
  Purchase #3 $109.77   12.145%   $123.1016   $123.10   $123.10   $123.10  
  Purchase #4 $100.71   9.401%   $110.1777   $110.18   $110.20   $110.20  
  Purchase #5 $202.39   3.500%   $209.4737   $209.47   $209.45   $209.50  
  Purchase #6 $227.72   10.527%   $251.6921   $251.69   $251.70   $251.70  
  Purchase #7 $148.72   5.689%   $157.1807   $157.18   $157.20   $157.20  
  7 purchase totals = $1,105.56       $1,205.8329   $1,205.83   $1,205.85   $1,205.90