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 $162.79   8.246%   $176.2137   $176.21   $176.20   $176.20  
  Purchase #2 $166.39   7.336%   $178.5964   $178.60   $178.60   $178.60  
  Purchase #3 $48.80   6.566%   $52.0042   $52.00   $52.00   $52.00  
  Purchase #4 $250.36   12.605%   $281.9179   $281.92   $281.90   $281.90  
  Purchase #5 $108.95   4.503%   $113.856   $113.86   $113.85   $113.90  
  Purchase #6 $104.48   4.609%   $109.2955   $109.30   $109.30   $109.30  
  Purchase #7 $175.97   7.534%   $189.2276   $189.23   $189.25   $189.20  
  7 purchase totals = $1,017.74       $1,101.1113   $1,101.12   $1,101.10   $1,101.10