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 $195.85   8.524%   $212.5443   $212.54   $212.55   $212.50  
  Purchase #2 $86.92   8.440%   $94.256   $94.26   $94.25   $94.30  
  Purchase #3 $38.60   3.395%   $39.9105   $39.91   $39.90   $39.90  
  Purchase #4 $62.48   11.529%   $69.6833   $69.68   $69.70   $69.70  
  Purchase #5 $150.27   9.831%   $165.043   $165.04   $165.05   $165.00  
  Purchase #6 $81.30   5.464%   $85.7422   $85.74   $85.75   $85.70  
  Purchase #7 $200.70   3.834%   $208.3948   $208.39   $208.40   $208.40  
  7 purchase totals = $816.12       $875.5741   $875.56   $875.60   $875.50