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 $214.41   10.751%   $237.4612   $237.46   $237.45   $237.50  
  Purchase #2 $115.65   12.138%   $129.6876   $129.69   $129.70   $129.70  
  Purchase #3 $68.54   7.840%   $73.9135   $73.91   $73.90   $73.90  
  Purchase #4 $98.27   4.873%   $103.0587   $103.06   $103.05   $103.10  
  Purchase #5 $58.39   12.283%   $65.562   $65.56   $65.55   $65.60  
  Purchase #6 $224.60   7.232%   $240.8431   $240.84   $240.85   $240.80  
  Purchase #7 $233.87   4.826%   $245.1566   $245.16   $245.15   $245.20  
  7 purchase totals = $1,013.73       $1,095.6827   $1,095.68   $1,095.65   $1,095.80