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 $214.66   4.407%   $224.1201   $224.12   $224.10   $224.10  
  Purchase #2 $210.62   9.573%   $230.7827   $230.78   $230.80   $230.80  
  Purchase #3 $94.96   13.257%   $107.5488   $107.55   $107.55   $107.50  
  Purchase #4 $5.50   9.578%   $6.0268   $6.03   $6.05   $6.00  
  Purchase #5 $222.51   9.376%   $243.3725   $243.37   $243.35   $243.40  
  Purchase #6 $187.49   8.234%   $202.9279   $202.93   $202.95   $202.90  
  Purchase #7 $217.90   13.540%   $247.4037   $247.40   $247.40   $247.40  
  7 purchase totals = $1,153.64       $1,262.1825   $1,262.18   $1,262.20   $1,262.10