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 $120.28   4.760%   $126.0053   $126.01   $126.00   $126.00  
  Purchase #2 $63.59   12.655%   $71.6373   $71.64   $71.65   $71.60  
  Purchase #3 $184.65   3.174%   $190.5108   $190.51   $190.50   $190.50  
  Purchase #4 $144.95   10.595%   $160.3075   $160.31   $160.30   $160.30  
  Purchase #5 $250.93   6.572%   $267.4211   $267.42   $267.40   $267.40  
  Purchase #6 $183.76   8.298%   $199.0084   $199.01   $199.00   $199.00  
  Purchase #7 $210.75   3.459%   $218.0398   $218.04   $218.05   $218.00  
  7 purchase totals = $1,158.91       $1,232.9302   $1,232.94   $1,232.90   $1,232.80