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 $185.70   9.300%   $202.9701   $202.97   $202.95   $203.00  
  Purchase #2 $74.26   11.342%   $82.6826   $82.68   $82.70   $82.70  
  Purchase #3 $205.25   4.281%   $214.0368   $214.04   $214.05   $214.00  
  Purchase #4 $93.60   13.796%   $106.5131   $106.51   $106.50   $106.50  
  Purchase #5 $131.84   6.757%   $140.7484   $140.75   $140.75   $140.70  
  Purchase #6 $231.43   3.272%   $239.0024   $239.00   $239.00   $239.00  
  Purchase #7 $111.28   6.173%   $118.1493   $118.15   $118.15   $118.10  
  7 purchase totals = $1,033.36       $1,104.1027   $1,104.10   $1,104.10   $1,104.00