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 $233.84   3.812%   $242.754   $242.75   $242.75   $242.80  
  Purchase #2 $77.43   11.763%   $86.5381   $86.54   $86.55   $86.50  
  Purchase #3 $125.87   3.730%   $130.565   $130.57   $130.55   $130.60  
  Purchase #4 $179.98   12.187%   $201.9142   $201.91   $201.90   $201.90  
  Purchase #5 $228.43   10.137%   $251.5859   $251.59   $251.60   $251.60  
  Purchase #6 $210.71   8.783%   $229.2167   $229.22   $229.20   $229.20  
  Purchase #7 $204.30   4.185%   $212.85   $212.85   $212.85   $212.90  
  7 purchase totals = $1,260.56       $1,355.4239   $1,355.43   $1,355.40   $1,355.50