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 $214.25   10.205%   $236.1142   $236.11   $236.10   $236.10  
  Purchase #2 $193.37   7.286%   $207.4589   $207.46   $207.45   $207.50  
  Purchase #3 $92.43   4.399%   $96.496   $96.50   $96.50   $96.50  
  Purchase #4 $18.97   5.466%   $20.0069   $20.01   $20.00   $20.00  
  Purchase #5 $179.60   12.392%   $201.856   $201.86   $201.85   $201.90  
  Purchase #6 $155.80   11.171%   $173.2044   $173.20   $173.20   $173.20  
  Purchase #7 $178.41   9.816%   $195.9227   $195.92   $195.90   $195.90  
  7 purchase totals = $1,032.83       $1,131.0591   $1,131.06   $1,131.00   $1,131.10