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 $195.86   9.570%   $214.6038   $214.60   $214.60   $214.60  
  Purchase #2 $46.42   5.139%   $48.8055   $48.81   $48.80   $48.80  
  Purchase #3 $146.90   13.829%   $167.2148   $167.21   $167.20   $167.20  
  Purchase #4 $38.89   11.802%   $43.4798   $43.48   $43.50   $43.50  
  Purchase #5 $178.89   3.586%   $185.305   $185.31   $185.30   $185.30  
  Purchase #6 $106.67   13.266%   $120.8208   $120.82   $120.80   $120.80  
  Purchase #7 $63.39   13.840%   $72.1632   $72.16   $72.15   $72.20  
  7 purchase totals = $777.02       $852.3929   $852.39   $852.35   $852.40