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 $202.93   4.267%   $211.589   $211.59   $211.60   $211.60  
  Purchase #2 $180.73   13.261%   $204.6966   $204.70   $204.70   $204.70  
  Purchase #3 $91.71   4.625%   $95.9516   $95.95   $95.95   $96.00  
  Purchase #4 $95.40   10.235%   $105.1642   $105.16   $105.15   $105.20  
  Purchase #5 $115.92   3.305%   $119.7512   $119.75   $119.75   $119.80  
  Purchase #6 $114.44   3.213%   $118.117   $118.12   $118.10   $118.10  
  Purchase #7 $90.80   13.696%   $103.236   $103.24   $103.25   $103.20  
  7 purchase totals = $891.93       $958.5056   $958.51   $958.50   $958.60