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 $61.85   9.126%   $67.4944   $67.49   $67.50   $67.50  
  Purchase #2 $91.77   3.816%   $95.2719   $95.27   $95.25   $95.30  
  Purchase #3 $100.50   6.345%   $106.8767   $106.88   $106.90   $106.90  
  Purchase #4 $236.36   11.422%   $263.357   $263.36   $263.35   $263.40  
  Purchase #5 $209.40   13.216%   $237.0743   $237.07   $237.05   $237.10  
  Purchase #6 $196.65   7.735%   $211.8609   $211.86   $211.85   $211.90  
  Purchase #7 $187.40   5.645%   $197.9787   $197.98   $198.00   $198.00  
  7 purchase totals = $1,083.93       $1,179.9139   $1,179.91   $1,179.90   $1,180.10