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 $35.68   4.661%   $37.343   $37.34   $37.35   $37.30  
  Purchase #2 $223.93   6.801%   $239.1595   $239.16   $239.15   $239.20  
  Purchase #3 $200.77   8.219%   $217.2713   $217.27   $217.25   $217.30  
  Purchase #4 $101.50   11.367%   $113.0375   $113.04   $113.05   $113.00  
  Purchase #5 $152.94   8.669%   $166.1984   $166.20   $166.20   $166.20  
  Purchase #6 $46.60   13.108%   $52.7083   $52.71   $52.70   $52.70  
  Purchase #7 $224.39   4.531%   $234.5571   $234.56   $234.55   $234.60  
  7 purchase totals = $985.81       $1,060.2751   $1,060.28   $1,060.25   $1,060.30