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 $201.54   3.360%   $208.3117   $208.31   $208.30   $208.30  
  Purchase #2 $44.91   7.117%   $48.1062   $48.11   $48.10   $48.10  
  Purchase #3 $39.60   4.695%   $41.4592   $41.46   $41.45   $41.50  
  Purchase #4 $101.88   7.265%   $109.2816   $109.28   $109.30   $109.30  
  Purchase #5 $230.87   9.205%   $252.1216   $252.12   $252.10   $252.10  
  Purchase #6 $116.37   13.218%   $131.7518   $131.75   $131.75   $131.80  
  Purchase #7 $245.78   6.791%   $262.4709   $262.47   $262.45   $262.50  
  7 purchase totals = $980.95       $1,053.5030   $1,053.50   $1,053.45   $1,053.60