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 $167.25   7.465%   $179.7352   $179.74   $179.75   $179.70  
  Purchase #2 $108.55   6.703%   $115.8261   $115.83   $115.85   $115.80  
  Purchase #3 $208.55   7.704%   $224.6167   $224.62   $224.60   $224.60  
  Purchase #4 $202.37   4.719%   $211.9198   $211.92   $211.90   $211.90  
  Purchase #5 $45.87   13.412%   $52.0221   $52.02   $52.00   $52.00  
  Purchase #6 $238.79   8.667%   $259.4859   $259.49   $259.50   $259.50  
  Purchase #7 $203.46   7.822%   $219.3746   $219.37   $219.35   $219.40  
  7 purchase totals = $1,174.84       $1,262.9804   $1,262.99   $1,262.95   $1,262.90