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 $167.75   11.479%   $187.006   $187.01   $187.00   $187.00  
  Purchase #2 $222.48   3.830%   $231.001   $231.00   $231.00   $231.00  
  Purchase #3 $119.93   6.866%   $128.1644   $128.16   $128.15   $128.20  
  Purchase #4 $233.28   12.258%   $261.8755   $261.88   $261.90   $261.90  
  Purchase #5 $226.29   6.190%   $240.2974   $240.30   $240.30   $240.30  
  Purchase #6 $158.28   4.666%   $165.6653   $165.67   $165.65   $165.70  
  Purchase #7 $193.39   13.136%   $218.7937   $218.79   $218.80   $218.80  
  7 purchase totals = $1,321.40       $1,432.8033   $1,432.81   $1,432.80   $1,432.90