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 $228.61   7.551%   $245.8723   $245.87   $245.85   $245.90  
  Purchase #2 $122.27   4.643%   $127.947   $127.95   $127.95   $127.90  
  Purchase #3 $24.69   4.516%   $25.805   $25.81   $25.80   $25.80  
  Purchase #4 $116.74   6.375%   $124.1822   $124.18   $124.20   $124.20  
  Purchase #5 $234.27   5.515%   $247.19   $247.19   $247.20   $247.20  
  Purchase #6 $187.75   4.643%   $196.4672   $196.47   $196.45   $196.50  
  Purchase #7 $215.47   7.801%   $232.2788   $232.28   $232.30   $232.30  
  7 purchase totals = $1,129.80       $1,199.7425   $1,199.75   $1,199.75   $1,199.80