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 $68.59   3.149%   $70.7499   $70.75   $70.75   $70.70  
  Purchase #2 $135.78   3.325%   $140.2947   $140.29   $140.30   $140.30  
  Purchase #3 $163.90   10.835%   $181.6586   $181.66   $181.65   $181.70  
  Purchase #4 $23.40   4.747%   $24.5108   $24.51   $24.50   $24.50  
  Purchase #5 $7.31   13.162%   $8.2721   $8.27   $8.25   $8.30  
  Purchase #6 $63.64   8.224%   $68.8738   $68.87   $68.85   $68.90  
  Purchase #7 $215.91   11.709%   $241.1909   $241.19   $241.20   $241.20  
  7 purchase totals = $678.53       $735.5508   $735.54   $735.50   $735.60