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 $230.39   5.791%   $243.7319   $243.73   $243.75   $243.70  
  Purchase #2 $239.36   6.418%   $254.7221   $254.72   $254.70   $254.70  
  Purchase #3 $166.91   6.580%   $177.8927   $177.89   $177.90   $177.90  
  Purchase #4 $102.91   13.143%   $116.4355   $116.44   $116.45   $116.40  
  Purchase #5 $83.62   12.765%   $94.2941   $94.29   $94.30   $94.30  
  Purchase #6 $112.55   6.287%   $119.626   $119.63   $119.65   $119.60  
  Purchase #7 $90.57   5.271%   $95.3439   $95.34   $95.35   $95.30  
  7 purchase totals = $1,026.31       $1,102.0462   $1,102.04   $1,102.10   $1,101.90