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 $158.84   5.128%   $166.9853   $166.99   $167.00   $167.00  
  Purchase #2 $86.29   8.237%   $93.3977   $93.40   $93.40   $93.40  
  Purchase #3 $231.82   4.358%   $241.9227   $241.92   $241.90   $241.90  
  Purchase #4 $69.46   4.434%   $72.5399   $72.54   $72.55   $72.50  
  Purchase #5 $211.34   4.250%   $220.322   $220.32   $220.30   $220.30  
  Purchase #6 $244.47   11.383%   $272.298   $272.30   $272.30   $272.30  
  Purchase #7 $132.87   10.759%   $147.1655   $147.17   $147.15   $147.20  
  7 purchase totals = $1,135.09       $1,214.6311   $1,214.64   $1,214.60   $1,214.60