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 $177.68   3.323%   $183.5843   $183.58   $183.60   $183.60  
  Purchase #2 $211.94   6.369%   $225.4385   $225.44   $225.45   $225.40  
  Purchase #3 $51.88   5.345%   $54.653   $54.65   $54.65   $54.70  
  Purchase #4 $125.46   7.295%   $134.6123   $134.61   $134.60   $134.60  
  Purchase #5 $141.41   8.488%   $153.4129   $153.41   $153.40   $153.40  
  Purchase #6 $221.65   9.502%   $242.7112   $242.71   $242.70   $242.70  
  Purchase #7 $172.26   5.638%   $181.972   $181.97   $181.95   $182.00  
  7 purchase totals = $1,102.28       $1,176.3842   $1,176.37   $1,176.35   $1,176.40