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 $185.56   5.796%   $196.3151   $196.32   $196.30   $196.30  
  Purchase #2 $223.63   5.577%   $236.1018   $236.10   $236.10   $236.10  
  Purchase #3 $247.56   3.491%   $256.2023   $256.20   $256.20   $256.20  
  Purchase #4 $159.92   9.403%   $174.9573   $174.96   $174.95   $175.00  
  Purchase #5 $167.91   9.574%   $183.9857   $183.99   $184.00   $184.00  
  Purchase #6 $172.96   11.350%   $192.591   $192.59   $192.60   $192.60  
  Purchase #7 $246.55   4.563%   $257.8001   $257.80   $257.80   $257.80  
  7 purchase totals = $1,404.09       $1,497.9533   $1,497.96   $1,497.95   $1,498.00