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 $12.46   13.326%   $14.1204   $14.12   $14.10   $14.10  
  Purchase #2 $59.43   12.137%   $66.643   $66.64   $66.65   $66.60  
  Purchase #3 $10.72   3.783%   $11.1255   $11.13   $11.15   $11.10  
  Purchase #4 $225.57   4.658%   $236.0771   $236.08   $236.10   $236.10  
  Purchase #5 $237.29   4.841%   $248.7772   $248.78   $248.80   $248.80  
  Purchase #6 $210.34   10.826%   $233.1114   $233.11   $233.10   $233.10  
  Purchase #7 $181.37   10.494%   $200.403   $200.40   $200.40   $200.40  
  7 purchase totals = $937.18       $1,010.2576   $1,010.26   $1,010.30   $1,010.20