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 $176.91   5.292%   $186.2721   $186.27   $186.25   $186.30  
  Purchase #2 $142.53   7.132%   $152.6952   $152.70   $152.70   $152.70  
  Purchase #3 $235.32   11.645%   $262.723   $262.72   $262.70   $262.70  
  Purchase #4 $49.33   6.500%   $52.5365   $52.54   $52.55   $52.50  
  Purchase #5 $213.56   8.865%   $232.4921   $232.49   $232.50   $232.50  
  Purchase #6 $70.95   11.349%   $79.0021   $79.00   $79.00   $79.00  
  Purchase #7 $56.73   4.507%   $59.2868   $59.29   $59.30   $59.30  
  7 purchase totals = $945.33       $1,025.0078   $1,025.01   $1,025.00   $1,025.00