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 $87.76   8.717%   $95.41   $95.41   $95.40   $95.40  
  Purchase #2 $118.66   3.735%   $123.092   $123.09   $123.10   $123.10  
  Purchase #3 $122.33   9.843%   $134.3709   $134.37   $134.35   $134.40  
  Purchase #4 $43.80   9.644%   $48.0241   $48.02   $48.00   $48.00  
  Purchase #5 $162.79   6.565%   $173.4772   $173.48   $173.50   $173.50  
  Purchase #6 $209.82   8.728%   $228.1331   $228.13   $228.15   $228.10  
  Purchase #7 $246.83   5.857%   $261.2868   $261.29   $261.30   $261.30  
  7 purchase totals = $991.99       $1,063.7941   $1,063.79   $1,063.80   $1,063.80