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 $183.98   4.710%   $192.6455   $192.65   $192.65   $192.60  
  Purchase #2 $166.42   9.135%   $181.6225   $181.62   $181.60   $181.60  
  Purchase #3 $62.58   10.451%   $69.1202   $69.12   $69.10   $69.10  
  Purchase #4 $114.39   5.235%   $120.3783   $120.38   $120.40   $120.40  
  Purchase #5 $241.31   8.749%   $262.4222   $262.42   $262.40   $262.40  
  Purchase #6 $31.86   11.273%   $35.4516   $35.45   $35.45   $35.50  
  Purchase #7 $182.31   10.550%   $201.5437   $201.54   $201.55   $201.50  
  7 purchase totals = $982.85       $1,063.1840   $1,063.18   $1,063.15   $1,063.10