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 $145.47   5.157%   $152.9719   $152.97   $152.95   $153.00  
  Purchase #2 $175.34   8.726%   $190.6402   $190.64   $190.65   $190.60  
  Purchase #3 $200.99   11.107%   $223.314   $223.31   $223.30   $223.30  
  Purchase #4 $73.32   13.169%   $82.9755   $82.98   $83.00   $83.00  
  Purchase #5 $212.57   7.527%   $228.5701   $228.57   $228.55   $228.60  
  Purchase #6 $171.58   13.204%   $194.2354   $194.24   $194.25   $194.20  
  Purchase #7 $179.29   4.603%   $187.5427   $187.54   $187.55   $187.50  
  7 purchase totals = $1,158.56       $1,260.2498   $1,260.25   $1,260.25   $1,260.20