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 $107.53   5.665%   $113.6216   $113.62   $113.60   $113.60  
  Purchase #2 $147.71   4.232%   $153.9611   $153.96   $153.95   $154.00  
  Purchase #3 $51.26   3.217%   $52.909   $52.91   $52.90   $52.90  
  Purchase #4 $157.93   13.453%   $179.1763   $179.18   $179.20   $179.20  
  Purchase #5 $208.38   8.727%   $226.5653   $226.57   $226.55   $226.60  
  Purchase #6 $96.32   5.865%   $101.9692   $101.97   $101.95   $102.00  
  Purchase #7 $181.82   9.246%   $198.6311   $198.63   $198.65   $198.60  
  7 purchase totals = $950.95       $1,026.8336   $1,026.84   $1,026.80   $1,026.90