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 $88.37   8.517%   $95.8965   $95.90   $95.90   $95.90  
  Purchase #2 $212.71   10.837%   $235.7614   $235.76   $235.75   $235.80  
  Purchase #3 $44.60   10.614%   $49.3338   $49.33   $49.35   $49.30  
  Purchase #4 $205.56   6.493%   $218.907   $218.91   $218.90   $218.90  
  Purchase #5 $117.69   7.307%   $126.2896   $126.29   $126.30   $126.30  
  Purchase #6 $250.39   9.688%   $274.6478   $274.65   $274.65   $274.60  
  Purchase #7 $137.83   10.642%   $152.4979   $152.50   $152.50   $152.50  
  7 purchase totals = $1,057.15       $1,153.3340   $1,153.34   $1,153.35   $1,153.30