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 $88.69   7.663%   $95.4863   $95.49   $95.50   $95.50  
  Purchase #2 $160.98   3.822%   $167.1327   $167.13   $167.15   $167.10  
  Purchase #3 $245.69   6.836%   $262.4854   $262.49   $262.50   $262.50  
  Purchase #4 $90.61   3.450%   $93.736   $93.74   $93.75   $93.70  
  Purchase #5 $81.54   8.872%   $88.7742   $88.77   $88.75   $88.80  
  Purchase #6 $249.42   10.713%   $276.1404   $276.14   $276.15   $276.10  
  Purchase #7 $151.86   7.721%   $163.5851   $163.59   $163.60   $163.60  
  7 purchase totals = $1,068.79       $1,147.3401   $1,147.35   $1,147.40   $1,147.30