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 $71.95   7.451%   $77.311   $77.31   $77.30   $77.30  
  Purchase #2 $244.26   4.257%   $254.6581   $254.66   $254.65   $254.70  
  Purchase #3 $87.68   9.584%   $96.0833   $96.08   $96.10   $96.10  
  Purchase #4 $149.42   12.241%   $167.7105   $167.71   $167.70   $167.70  
  Purchase #5 $125.75   13.665%   $142.9337   $142.93   $142.95   $142.90  
  Purchase #6 $235.55   11.541%   $262.7348   $262.73   $262.75   $262.70  
  Purchase #7 $190.64   5.568%   $201.2548   $201.25   $201.25   $201.30  
  7 purchase totals = $1,105.25       $1,202.6862   $1,202.67   $1,202.70   $1,202.70