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 $180.63   11.624%   $201.6264   $201.63   $201.65   $201.60  
  Purchase #2 $173.36   6.835%   $185.2092   $185.21   $185.20   $185.20  
  Purchase #3 $31.40   11.865%   $35.1256   $35.13   $35.15   $35.10  
  Purchase #4 $134.40   12.573%   $151.2981   $151.30   $151.30   $151.30  
  Purchase #5 $213.90   8.614%   $232.3253   $232.33   $232.35   $232.30  
  Purchase #6 $151.65   6.299%   $161.2024   $161.20   $161.20   $161.20  
  Purchase #7 $144.40   10.450%   $159.4898   $159.49   $159.50   $159.50  
  7 purchase totals = $1,029.74       $1,126.2768   $1,126.29   $1,126.35   $1,126.20