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 $182.69   7.715%   $196.7845   $196.78   $196.80   $196.80  
  Purchase #2 $226.62   6.632%   $241.6494   $241.65   $241.65   $241.60  
  Purchase #3 $159.67   5.113%   $167.8339   $167.83   $167.85   $167.80  
  Purchase #4 $75.33   8.752%   $81.9229   $81.92   $81.90   $81.90  
  Purchase #5 $217.57   4.793%   $227.9981   $228.00   $228.00   $228.00  
  Purchase #6 $94.60   13.741%   $107.599   $107.60   $107.60   $107.60  
  Purchase #7 $137.35   10.725%   $152.0808   $152.08   $152.10   $152.10  
  7 purchase totals = $1,093.83       $1,175.8686   $1,175.86   $1,175.90   $1,175.80