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 $185.69   8.398%   $201.2842   $201.28   $201.30   $201.30  
  Purchase #2 $224.41   4.125%   $233.6669   $233.67   $233.65   $233.70  
  Purchase #3 $84.26   7.381%   $90.4792   $90.48   $90.50   $90.50  
  Purchase #4 $141.40   10.516%   $156.2696   $156.27   $156.25   $156.30  
  Purchase #5 $202.68   11.841%   $226.6793   $226.68   $226.70   $226.70  
  Purchase #6 $179.43   5.867%   $189.9572   $189.96   $189.95   $190.00  
  Purchase #7 $25.26   9.501%   $27.66   $27.66   $27.65   $27.70  
  7 purchase totals = $1,043.13       $1,125.9964   $1,126.00   $1,126.00   $1,126.20