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 $152.53   9.585%   $167.15   $167.15   $167.15   $167.20  
  Purchase #2 $187.47   9.536%   $205.3471   $205.35   $205.35   $205.30  
  Purchase #3 $210.99   10.493%   $233.1292   $233.13   $233.15   $233.10  
  Purchase #4 $30.31   7.603%   $32.6145   $32.61   $32.60   $32.60  
  Purchase #5 $142.54   9.833%   $156.556   $156.56   $156.55   $156.60  
  Purchase #6 $42.92   10.582%   $47.4618   $47.46   $47.45   $47.50  
  Purchase #7 $226.41   3.801%   $235.0158   $235.02   $235.00   $235.00  
  7 purchase totals = $993.17       $1,077.2744   $1,077.28   $1,077.25   $1,077.30