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 $43.96   4.696%   $46.0244   $46.02   $46.00   $46.00  
  Purchase #2 $97.59   6.755%   $104.1822   $104.18   $104.20   $104.20  
  Purchase #3 $241.99   4.463%   $252.79   $252.79   $252.80   $252.80  
  Purchase #4 $196.71   7.109%   $210.6941   $210.69   $210.70   $210.70  
  Purchase #5 $116.63   13.584%   $132.473   $132.47   $132.45   $132.50  
  Purchase #6 $149.55   4.419%   $156.1586   $156.16   $156.15   $156.20  
  Purchase #7 $181.74   12.171%   $203.8596   $203.86   $203.85   $203.90  
  7 purchase totals = $1,028.17       $1,106.1819   $1,106.17   $1,106.15   $1,106.30