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 $184.85   8.578%   $200.7064   $200.71   $200.70   $200.70  
  Purchase #2 $99.84   11.489%   $111.3106   $111.31   $111.30   $111.30  
  Purchase #3 $10.50   5.752%   $11.104   $11.10   $11.10   $11.10  
  Purchase #4 $248.98   5.829%   $263.493   $263.49   $263.50   $263.50  
  Purchase #5 $209.86   6.797%   $224.1242   $224.12   $224.10   $224.10  
  Purchase #6 $57.98   3.523%   $60.0226   $60.02   $60.00   $60.00  
  Purchase #7 $177.44   8.579%   $192.6626   $192.66   $192.65   $192.70  
  7 purchase totals = $989.45       $1,063.4234   $1,063.41   $1,063.35   $1,063.40