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 $189.59   8.240%   $205.2122   $205.21   $205.20   $205.20  
  Purchase #2 $185.99   6.623%   $198.3081   $198.31   $198.30   $198.30  
  Purchase #3 $223.68   5.188%   $235.2845   $235.28   $235.30   $235.30  
  Purchase #4 $84.85   7.422%   $91.1476   $91.15   $91.15   $91.10  
  Purchase #5 $130.49   8.426%   $141.4851   $141.49   $141.50   $141.50  
  Purchase #6 $77.25   5.213%   $81.277   $81.28   $81.30   $81.30  
  Purchase #7 $56.58   9.289%   $61.8357   $61.84   $61.85   $61.80  
  7 purchase totals = $948.43       $1,014.5502   $1,014.56   $1,014.60   $1,014.50