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 $236.89   3.204%   $244.48   $244.48   $244.50   $244.50  
  Purchase #2 $90.55   7.296%   $97.1565   $97.16   $97.15   $97.20  
  Purchase #3 $206.59   7.445%   $221.9706   $221.97   $221.95   $222.00  
  Purchase #4 $218.88   6.692%   $233.5274   $233.53   $233.55   $233.50  
  Purchase #5 $169.98   3.697%   $176.2642   $176.26   $176.25   $176.30  
  Purchase #6 $212.72   9.313%   $232.5306   $232.53   $232.55   $232.50  
  Purchase #7 $127.59   8.332%   $138.2208   $138.22   $138.20   $138.20  
  7 purchase totals = $1,263.20       $1,344.1501   $1,344.15   $1,344.15   $1,344.20