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 $60.98   3.864%   $63.3363   $63.34   $63.35   $63.30  
  Purchase #2 $236.54   13.785%   $269.147   $269.15   $269.15   $269.10  
  Purchase #3 $141.32   10.697%   $156.437   $156.44   $156.45   $156.40  
  Purchase #4 $172.46   9.252%   $188.416   $188.42   $188.40   $188.40  
  Purchase #5 $217.85   10.823%   $241.4279   $241.43   $241.45   $241.40  
  Purchase #6 $170.64   3.111%   $175.9486   $175.95   $175.95   $175.90  
  Purchase #7 $56.35   9.441%   $61.67   $61.67   $61.65   $61.70  
  7 purchase totals = $1,056.14       $1,156.3828   $1,156.40   $1,156.40   $1,156.20