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 $208.80   12.724%   $235.3677   $235.37   $235.35   $235.40  
  Purchase #2 $205.92   6.450%   $219.2018   $219.20   $219.20   $219.20  
  Purchase #3 $150.50   11.238%   $167.4132   $167.41   $167.40   $167.40  
  Purchase #4 $55.56   7.527%   $59.742   $59.74   $59.75   $59.70  
  Purchase #5 $94.96   7.675%   $102.2482   $102.25   $102.25   $102.20  
  Purchase #6 $125.88   9.163%   $137.4144   $137.41   $137.40   $137.40  
  Purchase #7 $131.60   12.143%   $147.5802   $147.58   $147.60   $147.60  
  7 purchase totals = $973.22       $1,068.9675   $1,068.96   $1,068.95   $1,068.90