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 $194.25   3.461%   $200.973   $200.97   $200.95   $201.00  
  Purchase #2 $240.62   10.650%   $266.246   $266.25   $266.25   $266.20  
  Purchase #3 $202.80   10.523%   $224.1406   $224.14   $224.15   $224.10  
  Purchase #4 $156.89   10.199%   $172.8912   $172.89   $172.90   $172.90  
  Purchase #5 $19.45   13.131%   $22.004   $22.00   $22.00   $22.00  
  Purchase #6 $5.42   13.504%   $6.1519   $6.15   $6.15   $6.20  
  Purchase #7 $90.32   6.462%   $96.1565   $96.16   $96.15   $96.20  
  7 purchase totals = $909.75       $988.5632   $988.56   $988.55   $988.60