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 $211.75   10.513%   $234.0113   $234.01   $234.00   $234.00  
  Purchase #2 $45.87   6.301%   $48.7603   $48.76   $48.75   $48.80  
  Purchase #3 $111.59   3.857%   $115.894   $115.89   $115.90   $115.90  
  Purchase #4 $146.85   4.333%   $153.213   $153.21   $153.20   $153.20  
  Purchase #5 $240.85   13.203%   $272.6494   $272.65   $272.65   $272.60  
  Purchase #6 $47.30   12.806%   $53.3572   $53.36   $53.35   $53.40  
  Purchase #7 $178.55   7.466%   $191.8805   $191.88   $191.90   $191.90  
  7 purchase totals = $982.76       $1,069.7657   $1,069.76   $1,069.75   $1,069.80