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 $96.66   7.658%   $104.0622   $104.06   $104.05   $104.10  
  Purchase #2 $26.71   9.695%   $29.2995   $29.30   $29.30   $29.30  
  Purchase #3 $158.55   5.369%   $167.0625   $167.06   $167.05   $167.10  
  Purchase #4 $73.28   3.820%   $76.0793   $76.08   $76.10   $76.10  
  Purchase #5 $212.68   4.242%   $221.7019   $221.70   $221.70   $221.70  
  Purchase #6 $156.62   3.452%   $162.0265   $162.03   $162.05   $162.00  
  Purchase #7 $170.98   13.646%   $194.3119   $194.31   $194.30   $194.30  
  7 purchase totals = $895.48       $954.5438   $954.54   $954.55   $954.60