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 $213.95   6.253%   $227.3283   $227.33   $227.35   $227.30  
  Purchase #2 $217.54   11.218%   $241.9436   $241.94   $241.95   $241.90  
  Purchase #3 $229.92   13.456%   $260.858   $260.86   $260.85   $260.90  
  Purchase #4 $157.66   11.828%   $176.308   $176.31   $176.30   $176.30  
  Purchase #5 $90.62   6.643%   $96.6399   $96.64   $96.65   $96.60  
  Purchase #6 $39.76   12.819%   $44.8568   $44.86   $44.85   $44.90  
  Purchase #7 $250.89   6.430%   $267.0222   $267.02   $267.00   $267.00  
  7 purchase totals = $1,200.34       $1,314.9568   $1,314.96   $1,314.95   $1,314.90