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 $193.31   4.294%   $201.6107   $201.61   $201.60   $201.60  
  Purchase #2 $175.76   11.576%   $196.106   $196.11   $196.10   $196.10  
  Purchase #3 $126.59   4.662%   $132.4916   $132.49   $132.50   $132.50  
  Purchase #4 $13.88   9.396%   $15.1842   $15.18   $15.20   $15.20  
  Purchase #5 $225.34   4.281%   $234.9868   $234.99   $235.00   $235.00  
  Purchase #6 $63.26   5.397%   $66.6741   $66.67   $66.65   $66.70  
  Purchase #7 $163.74   9.829%   $179.834   $179.83   $179.85   $179.80  
  7 purchase totals = $961.88       $1,026.8874   $1,026.88   $1,026.90   $1,026.90