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 $174.67   12.550%   $196.5911   $196.59   $196.60   $196.60  
  Purchase #2 $236.77   3.197%   $244.3395   $244.34   $244.35   $244.30  
  Purchase #3 $248.55   8.286%   $269.1449   $269.14   $269.15   $269.10  
  Purchase #4 $173.62   4.739%   $181.8479   $181.85   $181.85   $181.80  
  Purchase #5 $9.33   3.275%   $9.6356   $9.64   $9.65   $9.60  
  Purchase #6 $103.51   6.618%   $110.3603   $110.36   $110.35   $110.40  
  Purchase #7 $64.79   5.677%   $68.4681   $68.47   $68.45   $68.50  
  7 purchase totals = $1,011.24       $1,080.3874   $1,080.39   $1,080.40   $1,080.30