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 $88.44   6.794%   $94.4486   $94.45   $94.45   $94.40  
  Purchase #2 $167.42   13.853%   $190.6127   $190.61   $190.60   $190.60  
  Purchase #3 $116.58   9.221%   $127.3298   $127.33   $127.35   $127.30  
  Purchase #4 $165.71   6.395%   $176.3072   $176.31   $176.30   $176.30  
  Purchase #5 $142.40   11.857%   $159.2844   $159.28   $159.30   $159.30  
  Purchase #6 $101.80   8.700%   $110.6566   $110.66   $110.65   $110.70  
  Purchase #7 $203.75   4.727%   $213.3813   $213.38   $213.40   $213.40  
  7 purchase totals = $986.10       $1,072.0206   $1,072.02   $1,072.05   $1,072.00