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 $202.68   5.713%   $214.2591   $214.26   $214.25   $214.30  
  Purchase #2 $104.94   8.252%   $113.5996   $113.60   $113.60   $113.60  
  Purchase #3 $58.50   5.180%   $61.5303   $61.53   $61.55   $61.50  
  Purchase #4 $109.27   12.381%   $122.7987   $122.80   $122.80   $122.80  
  Purchase #5 $233.85   10.454%   $258.2967   $258.30   $258.30   $258.30  
  Purchase #6 $109.34   6.595%   $116.551   $116.55   $116.55   $116.60  
  Purchase #7 $228.60   12.634%   $257.4813   $257.48   $257.50   $257.50  
  7 purchase totals = $1,047.18       $1,144.5167   $1,144.52   $1,144.55   $1,144.60