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 $207.41   4.119%   $215.9532   $215.95   $215.95   $216.00  
  Purchase #2 $104.42   8.388%   $113.1787   $113.18   $113.20   $113.20  
  Purchase #3 $203.25   8.147%   $219.8088   $219.81   $219.80   $219.80  
  Purchase #4 $235.52   5.201%   $247.7694   $247.77   $247.75   $247.80  
  Purchase #5 $148.87   5.541%   $157.1189   $157.12   $157.10   $157.10  
  Purchase #6 $217.88   11.265%   $242.4242   $242.42   $242.40   $242.40  
  Purchase #7 $57.25   4.109%   $59.6024   $59.60   $59.60   $59.60  
  7 purchase totals = $1,174.60       $1,255.8556   $1,255.85   $1,255.80   $1,255.90