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 $58.31   8.351%   $63.1795   $63.18   $63.20   $63.20  
  Purchase #2 $240.29   5.670%   $253.9144   $253.91   $253.90   $253.90  
  Purchase #3 $160.70   9.758%   $176.3811   $176.38   $176.40   $176.40  
  Purchase #4 $181.93   5.255%   $191.4904   $191.49   $191.50   $191.50  
  Purchase #5 $22.49   12.105%   $25.2124   $25.21   $25.20   $25.20  
  Purchase #6 $223.82   6.626%   $238.6503   $238.65   $238.65   $238.70  
  Purchase #7 $62.34   5.524%   $65.7837   $65.78   $65.80   $65.80  
  7 purchase totals = $949.88       $1,014.6118   $1,014.60   $1,014.65   $1,014.70