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 $152.47   9.532%   $167.0034   $167.00   $167.00   $167.00  
  Purchase #2 $189.81   10.218%   $209.2048   $209.20   $209.20   $209.20  
  Purchase #3 $57.55   9.863%   $63.2262   $63.23   $63.25   $63.20  
  Purchase #4 $90.91   5.214%   $95.65   $95.65   $95.65   $95.70  
  Purchase #5 $134.73   11.534%   $150.2698   $150.27   $150.25   $150.30  
  Purchase #6 $173.73   12.246%   $195.005   $195.01   $195.00   $195.00  
  Purchase #7 $51.32   3.465%   $53.0982   $53.10   $53.10   $53.10  
  7 purchase totals = $850.52       $933.4574   $933.46   $933.45   $933.50