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 $85.70   10.434%   $94.6419   $94.64   $94.65   $94.60  
  Purchase #2 $201.92   3.836%   $209.6657   $209.67   $209.65   $209.70  
  Purchase #3 $59.90   4.736%   $62.7369   $62.74   $62.75   $62.70  
  Purchase #4 $71.29   9.170%   $77.8273   $77.83   $77.85   $77.80  
  Purchase #5 $10.81   5.697%   $11.4258   $11.43   $11.45   $11.40  
  Purchase #6 $143.79   5.175%   $151.2311   $151.23   $151.25   $151.20  
  Purchase #7 $109.96   4.706%   $115.1347   $115.13   $115.15   $115.10  
  7 purchase totals = $683.37       $722.6634   $722.67   $722.75   $722.50