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 $82.29   4.828%   $86.263   $86.26   $86.25   $86.30  
  Purchase #2 $195.98   8.432%   $212.505   $212.51   $212.50   $212.50  
  Purchase #3 $103.41   3.268%   $106.7894   $106.79   $106.80   $106.80  
  Purchase #4 $121.75   7.321%   $130.6633   $130.66   $130.65   $130.70  
  Purchase #5 $130.97   12.481%   $147.3164   $147.32   $147.30   $147.30  
  Purchase #6 $205.85   9.584%   $225.5787   $225.58   $225.60   $225.60  
  Purchase #7 $143.29   11.338%   $159.5362   $159.54   $159.55   $159.50  
  7 purchase totals = $983.54       $1,068.6520   $1,068.66   $1,068.65   $1,068.70