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 $171.26   13.380%   $194.1746   $194.17   $194.15   $194.20  
  Purchase #2 $51.92   5.179%   $54.6089   $54.61   $54.60   $54.60  
  Purchase #3 $59.36   6.342%   $63.1246   $63.12   $63.10   $63.10  
  Purchase #4 $142.34   11.573%   $158.813   $158.81   $158.80   $158.80  
  Purchase #5 $231.30   11.861%   $258.7345   $258.73   $258.75   $258.70  
  Purchase #6 $226.35   3.452%   $234.1636   $234.16   $234.15   $234.20  
  Purchase #7 $39.87   4.764%   $41.7694   $41.77   $41.75   $41.80  
  7 purchase totals = $922.40       $1,005.3886   $1,005.37   $1,005.30   $1,005.40