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 $182.40   7.162%   $195.4635   $195.46   $195.45   $195.50  
  Purchase #2 $195.98   8.599%   $212.8323   $212.83   $212.85   $212.80  
  Purchase #3 $118.94   12.184%   $133.4316   $133.43   $133.45   $133.40  
  Purchase #4 $166.97   3.834%   $173.3716   $173.37   $173.35   $173.40  
  Purchase #5 $222.54   13.567%   $252.732   $252.73   $252.75   $252.70  
  Purchase #6 $210.90   12.241%   $236.7163   $236.72   $236.70   $236.70  
  Purchase #7 $57.73   12.796%   $65.1171   $65.12   $65.10   $65.10  
  7 purchase totals = $1,155.46       $1,269.6644   $1,269.66   $1,269.65   $1,269.60