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 $63.90   12.178%   $71.6817   $71.68   $71.70   $71.70  
  Purchase #2 $92.52   3.544%   $95.7989   $95.80   $95.80   $95.80  
  Purchase #3 $179.92   10.149%   $198.1801   $198.18   $198.20   $198.20  
  Purchase #4 $56.56   6.478%   $60.224   $60.22   $60.20   $60.20  
  Purchase #5 $85.75   6.831%   $91.6076   $91.61   $91.60   $91.60  
  Purchase #6 $74.86   9.155%   $81.7134   $81.71   $81.70   $81.70  
  Purchase #7 $101.77   4.426%   $106.2743   $106.27   $106.25   $106.30  
  7 purchase totals = $655.28       $705.4800   $705.47   $705.45   $705.50