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 $116.42   8.144%   $125.9012   $125.90   $125.90   $125.90  
  Purchase #2 $233.85   7.805%   $252.102   $252.10   $252.10   $252.10  
  Purchase #3 $106.26   8.731%   $115.5376   $115.54   $115.55   $115.50  
  Purchase #4 $167.73   5.540%   $177.0222   $177.02   $177.00   $177.00  
  Purchase #5 $53.37   5.607%   $56.3625   $56.36   $56.35   $56.40  
  Purchase #6 $217.62   12.396%   $244.5962   $244.60   $244.60   $244.60  
  Purchase #7 $89.36   9.249%   $97.6249   $97.62   $97.60   $97.60  
  7 purchase totals = $984.61       $1,069.1466   $1,069.14   $1,069.10   $1,069.10