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 $176.36   11.280%   $196.2534   $196.25   $196.25   $196.30  
  Purchase #2 $181.33   9.717%   $198.9498   $198.95   $198.95   $198.90  
  Purchase #3 $83.84   11.343%   $93.35   $93.35   $93.35   $93.40  
  Purchase #4 $195.87   3.154%   $202.0477   $202.05   $202.05   $202.00  
  Purchase #5 $136.85   11.543%   $152.6466   $152.65   $152.65   $152.60  
  Purchase #6 $95.56   8.460%   $103.6444   $103.64   $103.65   $103.60  
  Purchase #7 $180.84   7.536%   $194.4681   $194.47   $194.45   $194.50  
  7 purchase totals = $1,050.65       $1,141.3600   $1,141.36   $1,141.35   $1,141.30