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 $55.64   7.194%   $59.6427   $59.64   $59.65   $59.60  
  Purchase #2 $190.39   13.580%   $216.245   $216.25   $216.25   $216.20  
  Purchase #3 $224.27   6.424%   $238.6771   $238.68   $238.70   $238.70  
  Purchase #4 $58.53   4.608%   $61.2271   $61.23   $61.25   $61.20  
  Purchase #5 $128.66   9.689%   $141.1259   $141.13   $141.15   $141.10  
  Purchase #6 $119.36   5.553%   $125.9881   $125.99   $126.00   $126.00  
  Purchase #7 $180.71   11.354%   $201.2278   $201.23   $201.25   $201.20  
  7 purchase totals = $957.56       $1,044.1337   $1,044.15   $1,044.25   $1,044.00