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 $201.84   7.523%   $217.0244   $217.02   $217.00   $217.00  
  Purchase #2 $163.93   10.595%   $181.2984   $181.30   $181.30   $181.30  
  Purchase #3 $244.70   9.200%   $267.2124   $267.21   $267.20   $267.20  
  Purchase #4 $220.60   12.806%   $248.85   $248.85   $248.85   $248.90  
  Purchase #5 $237.61   5.575%   $250.8568   $250.86   $250.85   $250.90  
  Purchase #6 $201.78   7.798%   $217.5148   $217.51   $217.50   $217.50  
  Purchase #7 $215.96   8.856%   $235.0854   $235.09   $235.10   $235.10  
  7 purchase totals = $1,486.42       $1,617.8422   $1,617.84   $1,617.80   $1,617.90