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 $208.25   11.527%   $232.255   $232.26   $232.25   $232.30  
  Purchase #2 $248.49   9.106%   $271.1175   $271.12   $271.10   $271.10  
  Purchase #3 $192.41   8.634%   $209.0227   $209.02   $209.00   $209.00  
  Purchase #4 $65.32   9.257%   $71.3667   $71.37   $71.35   $71.40  
  Purchase #5 $145.67   9.113%   $158.9449   $158.94   $158.95   $158.90  
  Purchase #6 $194.84   12.118%   $218.4507   $218.45   $218.45   $218.50  
  Purchase #7 $244.34   7.349%   $262.2965   $262.30   $262.30   $262.30  
  7 purchase totals = $1,299.32       $1,423.4540   $1,423.46   $1,423.40   $1,423.50