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 $64.69   7.325%   $69.4285   $69.43   $69.45   $69.40  
  Purchase #2 $225.72   4.412%   $235.6788   $235.68   $235.70   $235.70  
  Purchase #3 $18.82   11.381%   $20.9619   $20.96   $20.95   $21.00  
  Purchase #4 $219.74   13.617%   $249.662   $249.66   $249.65   $249.70  
  Purchase #5 $96.63   6.112%   $102.536   $102.54   $102.55   $102.50  
  Purchase #6 $173.82   12.803%   $196.0742   $196.07   $196.05   $196.10  
  Purchase #7 $193.52   5.430%   $204.0281   $204.03   $204.05   $204.00  
  7 purchase totals = $992.94       $1,078.3695   $1,078.37   $1,078.40   $1,078.40