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 $71.94   4.190%   $74.9543   $74.95   $74.95   $75.00  
  Purchase #2 $188.64   4.229%   $196.6176   $196.62   $196.60   $196.60  
  Purchase #3 $222.69   4.748%   $233.2633   $233.26   $233.25   $233.30  
  Purchase #4 $106.88   3.225%   $110.3269   $110.33   $110.35   $110.30  
  Purchase #5 $21.97   12.745%   $24.7701   $24.77   $24.75   $24.80  
  Purchase #6 $88.76   7.569%   $95.4782   $95.48   $95.50   $95.50  
  Purchase #7 $102.53   3.871%   $106.4989   $106.50   $106.50   $106.50  
  7 purchase totals = $803.41       $841.9093   $841.91   $841.90   $842.00