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 $71.42   6.351%   $75.9559   $75.96   $75.95   $76.00  
  Purchase #2 $163.60   12.308%   $183.7359   $183.74   $183.75   $183.70  
  Purchase #3 $197.55   4.339%   $206.1217   $206.12   $206.10   $206.10  
  Purchase #4 $186.85   9.399%   $204.412   $204.41   $204.40   $204.40  
  Purchase #5 $248.58   11.636%   $277.5048   $277.50   $277.50   $277.50  
  Purchase #6 $230.91   6.795%   $246.6003   $246.60   $246.60   $246.60  
  Purchase #7 $153.75   5.423%   $162.0879   $162.09   $162.10   $162.10  
  7 purchase totals = $1,252.66       $1,356.4185   $1,356.42   $1,356.40   $1,356.40