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 $41.50   6.158%   $44.0556   $44.06   $44.05   $44.10  
  Purchase #2 $69.65   7.620%   $74.9573   $74.96   $74.95   $75.00  
  Purchase #3 $91.44   5.149%   $96.1482   $96.15   $96.15   $96.10  
  Purchase #4 $196.59   3.368%   $203.2112   $203.21   $203.20   $203.20  
  Purchase #5 $180.89   3.179%   $186.6405   $186.64   $186.65   $186.60  
  Purchase #6 $90.29   9.161%   $98.5615   $98.56   $98.55   $98.60  
  Purchase #7 $84.64   5.158%   $89.0057   $89.01   $89.00   $89.00  
  7 purchase totals = $755.00       $792.5800   $792.59   $792.55   $792.60