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 $60.88   11.262%   $67.7363   $67.74   $67.75   $67.70  
  Purchase #2 $140.74   4.854%   $147.5715   $147.57   $147.55   $147.60  
  Purchase #3 $56.83   4.506%   $59.3908   $59.39   $59.40   $59.40  
  Purchase #4 $208.41   13.155%   $235.8263   $235.83   $235.85   $235.80  
  Purchase #5 $201.89   13.849%   $229.8497   $229.85   $229.85   $229.80  
  Purchase #6 $224.96   8.352%   $243.7487   $243.75   $243.75   $243.70  
  Purchase #7 $195.70   11.179%   $217.5773   $217.58   $217.60   $217.60  
  7 purchase totals = $1,089.41       $1,201.7006   $1,201.71   $1,201.75   $1,201.60