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 $83.35   11.183%   $92.671   $92.67   $92.65   $92.70  
  Purchase #2 $132.28   13.185%   $149.7211   $149.72   $149.70   $149.70  
  Purchase #3 $208.61   12.122%   $233.8977   $233.90   $233.90   $233.90  
  Purchase #4 $168.77   9.654%   $185.0631   $185.06   $185.05   $185.10  
  Purchase #5 $16.48   9.255%   $18.0052   $18.01   $18.00   $18.00  
  Purchase #6 $223.55   5.597%   $236.0621   $236.06   $236.05   $236.10  
  Purchase #7 $92.36   4.637%   $96.6427   $96.64   $96.65   $96.60  
  7 purchase totals = $925.40       $1,012.0629   $1,012.06   $1,012.00   $1,012.10