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 $49.42   5.864%   $52.318   $52.32   $52.30   $52.30  
  Purchase #2 $246.78   4.370%   $257.5643   $257.56   $257.55   $257.60  
  Purchase #3 $140.63   8.372%   $152.4035   $152.40   $152.40   $152.40  
  Purchase #4 $239.80   8.518%   $260.2262   $260.23   $260.25   $260.20  
  Purchase #5 $241.98   12.406%   $272   $272.00   $272.00   $272.00  
  Purchase #6 $5.50   3.352%   $5.6844   $5.68   $5.70   $5.70  
  Purchase #7 $95.45   11.188%   $106.1289   $106.13   $106.15   $106.10  
  7 purchase totals = $1,019.56       $1,106.3253   $1,106.32   $1,106.35   $1,106.30