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 $196.84   5.482%   $207.6308   $207.63   $207.65   $207.60  
  Purchase #2 $38.64   8.130%   $41.7814   $41.78   $41.80   $41.80  
  Purchase #3 $69.53   11.106%   $77.252   $77.25   $77.25   $77.30  
  Purchase #4 $37.56   11.689%   $41.9504   $41.95   $41.95   $42.00  
  Purchase #5 $56.69   9.658%   $62.1651   $62.17   $62.15   $62.20  
  Purchase #6 $149.35   5.294%   $157.2566   $157.26   $157.25   $157.30  
  Purchase #7 $204.40   12.432%   $229.811   $229.81   $229.80   $229.80  
  7 purchase totals = $753.01       $817.8473   $817.85   $817.85   $818.00