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 $152.67   3.470%   $157.9676   $157.97   $157.95   $158.00  
  Purchase #2 $241.47   4.134%   $251.4524   $251.45   $251.45   $251.50  
  Purchase #3 $55.38   5.471%   $58.4098   $58.41   $58.40   $58.40  
  Purchase #4 $11.79   11.341%   $13.1271   $13.13   $13.15   $13.10  
  Purchase #5 $247.27   5.236%   $260.2171   $260.22   $260.20   $260.20  
  Purchase #6 $162.53   11.553%   $181.3071   $181.31   $181.30   $181.30  
  Purchase #7 $158.40   9.488%   $173.429   $173.43   $173.45   $173.40  
  7 purchase totals = $1,029.51       $1,095.9101   $1,095.92   $1,095.90   $1,095.90