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 $211.27   10.260%   $232.9463   $232.95   $232.95   $232.90  
  Purchase #2 $203.95   6.838%   $217.8961   $217.90   $217.90   $217.90  
  Purchase #3 $41.51   7.637%   $44.6801   $44.68   $44.70   $44.70  
  Purchase #4 $129.81   8.561%   $140.923   $140.92   $140.90   $140.90  
  Purchase #5 $71.96   4.628%   $75.2903   $75.29   $75.30   $75.30  
  Purchase #6 $205.44   6.133%   $218.0396   $218.04   $218.05   $218.00  
  Purchase #7 $125.75   3.516%   $130.1714   $130.17   $130.15   $130.20  
  7 purchase totals = $989.69       $1,059.9468   $1,059.95   $1,059.95   $1,059.90