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 $58.27   12.576%   $65.598   $65.60   $65.60   $65.60  
  Purchase #2 $195.84   6.550%   $208.6675   $208.67   $208.65   $208.70  
  Purchase #3 $184.25   5.574%   $194.5201   $194.52   $194.50   $194.50  
  Purchase #4 $54.26   6.133%   $57.5878   $57.59   $57.60   $57.60  
  Purchase #5 $98.60   8.252%   $106.7365   $106.74   $106.75   $106.70  
  Purchase #6 $246.84   6.155%   $262.033   $262.03   $262.05   $262.00  
  Purchase #7 $151.60   11.176%   $168.5428   $168.54   $168.55   $168.50  
  7 purchase totals = $989.66       $1,063.6857   $1,063.69   $1,063.70   $1,063.60