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 $92.82   3.425%   $95.9991   $96.00   $96.00   $96.00  
  Purchase #2 $140.80   9.832%   $154.6435   $154.64   $154.65   $154.60  
  Purchase #3 $230.73   4.791%   $241.7843   $241.78   $241.80   $241.80  
  Purchase #4 $228.67   10.854%   $253.4898   $253.49   $253.50   $253.50  
  Purchase #5 $25.48   4.727%   $26.6844   $26.68   $26.70   $26.70  
  Purchase #6 $208.42   8.701%   $226.5546   $226.55   $226.55   $226.60  
  Purchase #7 $48.73   11.756%   $54.4587   $54.46   $54.45   $54.50  
  7 purchase totals = $975.65       $1,053.6144   $1,053.60   $1,053.65   $1,053.70