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 $64.53   5.468%   $68.0585   $68.06   $68.05   $68.10  
  Purchase #2 $116.51   7.789%   $125.585   $125.59   $125.60   $125.60  
  Purchase #3 $174.91   7.859%   $188.6562   $188.66   $188.65   $188.70  
  Purchase #4 $182.52   4.596%   $190.9086   $190.91   $190.90   $190.90  
  Purchase #5 $184.49   8.391%   $199.9706   $199.97   $199.95   $200.00  
  Purchase #6 $243.90   11.484%   $271.9095   $271.91   $271.90   $271.90  
  Purchase #7 $167.29   5.608%   $176.6716   $176.67   $176.65   $176.70  
  7 purchase totals = $1,134.15       $1,221.7600   $1,221.77   $1,221.70   $1,221.90