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 $188.69   7.473%   $202.7908   $202.79   $202.80   $202.80  
  Purchase #2 $229.34   4.799%   $240.346   $240.35   $240.35   $240.30  
  Purchase #3 $211.45   12.168%   $237.1792   $237.18   $237.20   $237.20  
  Purchase #4 $23.46   12.552%   $26.4047   $26.40   $26.40   $26.40  
  Purchase #5 $156.85   4.365%   $163.6965   $163.70   $163.70   $163.70  
  Purchase #6 $100.93   5.545%   $106.5266   $106.53   $106.55   $106.50  
  Purchase #7 $215.65   5.820%   $228.2008   $228.20   $228.20   $228.20  
  7 purchase totals = $1,126.37       $1,205.1446   $1,205.15   $1,205.20   $1,205.10